Technical Corrosion Collaboration (TCC)
Research Projects at the University of Akron 2014
Fiscal Year 2014: United States Air Force Academy
Project Title
Analysis and Evaluation of Tropic-environment based on
Natural-exposure versus Accelerating Testing by following the
Damage Evolution Concept
Inert Atmospheric Plasma Polymerization (IAP) for Improved
Corrosion Protection
A Collaborative Agreement Between The University of Akron
and U.S. Military Academy at West Point to Develop and Verify
Localized Corrosion
Development of a Numerical Framework for Prediction of
Hydrogen-Induced Stress-Corrosion Cracking
Principle Investigator
H. Castaneda
A. Dhinojwala
G. Young
X. Gao
Project Title: Analysis and Evaluation of tropic-environment based on Natural-exposure versus Accelerating
Testing by following the Damage Evolution Concept
Principle Investigator: H. Castaneda and S. Louscher
Work Statement: The Continental United States (CONUS) does not have a natural deep-tropical environment.
Although there are some DoD test sites in Hawaii and Okinawa that provide somewhat similar conditions, the
majority of all natural tropic testing is performed in collaboration with host nations developing parts of the
world with the right harsh environment. These sites have been characterized by ARO (King et al, 2006 and
King et al., 2007) and are identified as the best tropic-analog locations for the U.S. government.
We are proposing to partner with TRTC to utilize the test assets that they maintain in
Panama to quantify the damage mechanisms through monitoring the damage evolution for different
materials, taking into account the spatial distribution of the degradation and the components of the
environment with time at the formed interfaces, and to conduct mechanistic analysis to assess the localized
occurrence and the damage evolution accumulation. Specifically, the following are the proposed objectives:
•
To design an experimental matrix and set up with physical prototypes exposed in tropical
environments that enables the characterization of the parameters that deteriorate the integrity of the
metallic, coated metallic and nonmetallic materials.
• To develop a database for the damage accumulation in different materials used for DoD assets in two
different environments (laboratory vs. nature tropical environment).
• To initiate a theoretical framework for damage evolution mechanisms that correlates environment vs.
performance based on metallic and nonmetallic materials degradation.
The conventional stages of the cumulative damage function of the metallic and coated metallic materials and
the damage mechanism assessment in the dynamic corrosive/aggressive environment can be characterized.
The damage function is based on the transport, activation, and degradation mechanisms existing during
exposure time in dynamic corrosive/aggressive environments; the physical characteristics of the system are
quantified by the current state of the materials to be exposed. The physical characteristics and the
environmental parameters could be analyzed with probability-statistical modeling approach; the physical
characteristics of the coated metallic surface, such as roughness, porosity, thickness, and the metallic localized
corrosion or nonmetallic substrates degradation linked with the stochastic nature of the environmental
parameters, such as preferential temperature, moisture, altitude, raining, UV, among other parameters.
The damage evolution
concept for materials includes three general stages describing the metallic substrate, metallic/protective layer
and the nonmetallic/environment interfaces as a result of degradation processes. The stages can be classified
according to transport, chemical degradation and/or electrochemical mechanisms. Initiation, active and
growth are stages that have been reported and we consider for the performance for different layer/metallic
and nonmetallic substrate. Each stage can be characterized by the mechanism existing at the surface, such as
the initiation stage, the active stage or growth stage can be a combination of solely one mechanism or many
different degradation mechanisms. The unique integration of field data with probability modeling to account
for the spatial and time distribution of water infiltration/interaction, temperature, moisture, location
influencing the surface materials and interfacial mechanisms over time will allow us to characterize the
degradation at different material/environment locations. Field testing can characterize the damage process
due to the interactions of aggressive species from the environment with surface properties and
probability/statistical modeling can quantify the effect of the environment. The material distribution
influences protective mechanisms that initiate upon exposure to a corrosive/aggressive environment. Our
proposal includes the development of a database and comprehensive method that will be obtained by
unifying field and laboratory testing determinations for the physical and chemical properties of the exposed
material with the random distribution nature of the environment that surrounds the selected material.
Task 1: Quantification, and characterization of transport and interfacial mechanisms for continuous
immersion in tropical conditions and wet-dry cyclic laboratory conditions.
Hypothesis: Use
the experimental design and standard characteristic methods to develop the mechanisms when natural and
induced cycling environmental conditions exist. Multiscale analysis unified with functions correlating
physical/chemical properties at the environment/surface can quantify the damage evolution of different
materials in tropical conditions.
Task 1 includes, materials selections, fundamental understanding, high resolution characterization and
elucidating of the degradation mechanisms, based upon combining chemical, physical properties using insight
from the literature and the prior art developed by our group in damage evolution characterization and high
resolution technologies. Task 1 consists of one overall task with four sub-tasks and lasts 24 months.
Task 1 Development of Refined Test Plan- Simple preparation Analysis and Report generation (months 24) for
Tropic conditions: Within 60 days after the award of the project, the NCERCAMP project team will work with
end users from DoD to develop a final project plan that includes:
•
A detailed matrix of sample materials to be exposed at each location along with a plan for obtaining
and preparing the samples
• A statement on the accelerated testing methodologies that will be utilized in the lab
• A procedural plan for field personnel responsible for deployment, photography, retrieval and return of
the sample materials
• A detailed description of the analysis methods
During this task of the project, field teams for the environmental exposure sites will actively deploy, track and
retrieve the samples in accordance with the procedures identified in Task 1.
Task 1.1 Baseline testing and mechanism characterization in physical prototype models. We will seek to
determine the transport, chemical and/or electrochemical mechanisms in different materials.
Representative Samples: The
tropical environment may degrade different materials via different mechanisms. Each set of samples
(9samples each in duplicate) will represent the characterization of the damage/degradation evolution with
time. Although the final sample matrix will be developed in consultation with DoD end users, NCERCAMP is
proposing to characterize the damage evolution in atmospheric conditions of the following materials.
Supplied by Research Team:
•
•
Polycarbonate (Standard Grade)
Polyacrylate (Standard Grade)
Fabric (Standard grade of polyester or other TBD commercial fabric representative of DoD tents) Non
Hexavalent- advanced coatings (based on MIL PRF 32239) on steel substrate
• Non Hexavalent- advanced coatings (based on MIL PRF 32239) on aluminum substrate
• Non Hexavalent coating on aluminum substrate 7076 T6 Aluminum substrate
• 2024T3 Aluminum substrate
• Steel low carbon AISI 1018
As part of the initial task of the study, the team will work with prospective DoD and industry partners to
confirm the sample matrix and obtain the relevant materials that are responsive to specific DoD needs.
•
The mechanisms will be characterized based on the damage evolution concept. The first stage considers a
transport, accumulation and effect of the aggressive species at the substrate/environment interface. The
second stage includes surface processes and chemical/physical/electrochemical reactions based on
degradation processes.
Task 1.2 Characterization of transport, accumulation and surface mechanisms: water infiltration, mass
transfer, sorption and physical/chemical degradation. The first baseline system formed by different
prototypes, such as metallic, coated metallic and nonmetallic materials exposed in tropical environments and
wet cyclic laboratory conditions. Nine selected materials will be exposed in tropical environments during 24
months; each material will include a 3 month period interval per sample for characterization.
The characterization of mechanisms will be obtained from systematic
experimental measurements of each material by using chemical and surface testing to obtain measurable
physical/chemical properties of the degradation/damage process. The samples will be designed to constrain
the exposed area in the required environment parameters determination of atmospheric parameters
(humidity, and ionic species) accumulation and degradation, electrochemical and mass transport mechanisms
at the interface level is elucidated and quantified by a combination of high resolution surface techniques
(SEM, IFM, AFM, SCEM Microscopy) at multiscale level and electrolyte dynamic evolution characterization.
Current and spatial potential profiles by SCEM will quantify the spatial distribution of current carrier (water) or
electrolyte influence on the degradation process. While the high resolution tools are used for
multidimensional analysis to reveal complex interdependent processes, spectroscopic tools are used for
electrolyte dynamics and higher scale [E. Maya et al 2014, Surface and Coating Technology Journal].
Task 1.3 Fundamental development of degradation mechanisms/materials for selected prototype systems.
Quantification of important parameters for different processes.
Following the
understanding and quantification of the transport and processes occurring at the samples surface in tropical
environment, the mechanisms are quantified by expressions in terms of critical parameters related to the
damage and physical/chemical properties.
Using previous surface accumulation
processes, transport mechanisms applied to degradation in metallic, coated metallic and nonmetallic materials
we will build upon the understanding developed in chemical, electrochemical degradation in metallic samples,
the water uptake transport and activation in the electrolyte-polymer and electrolyte-nonmetallic interactions,
extended by physical characterization of high resolution techniques. For each prototype including alloy
substrate/coating system, metallic and nonmetallic spatial physical conditions due to degradation effects are
correlated with the proper mechanisms at the required interface. The transport, surface reactions and current
time [V. Baukh, et al. NMR Imaging of Water in Multilayer Polymeric Films: Stressing the Role of Mechanical
Stress. Macromolecules, 2010].
Task 1.4 Statistical/probability development for damage mechanisms associated with the electrolyte
properties (wettability, chlorides, temperature, ionic content) for the physical prototype systems
Our previous damage evolution approach involved the spatial transport within the solid state formed by the
primer coating [J. Niu at el. J. of Coatings Technology and Research 2013]; the inorganic coating and the
substance consider different transport mechanisms and chemical/electrochemical damage processes. Most of
the previous work reported for organic coatings relates to the water uptake, and the damage of metallic
structures that considers stochastic and random distribution of damage due to localized attack (pitting), both
quantification has been done by using simple semi-empirical expressions with no consideration of corrosive
precursor vs. performance. By using the environment and sample measurements/characterization, the
quantification of damage mechanisms will be conducted by correlating the physical properties for the samples
with the state of the damage and the effect of the tropical environment. Surface testing by AFM (Atomic
Force Microscopy) will characterize the spatial potential/current and surface distribution of the damage
distribution due to the environmental exposure at each material. The probability distribution functions of
different physical parameters important for the material performance will be generated by the experimental
testing and will generate semi-empirical and functional relationships. The unification of probabilistic and
deterministic modeling will be based on the quantification and characterization of phenomenological
parameters, such as surface damage, potential profile, corrosion products (for metallic samples), capacitance
or impedance (for coated metallic samples) with inherent parameters of the system, such as crystalline
structure, hydrophobicity, chemical content (binders and pigments) to improve the rationalization of
theoretical-performance properties. Previously we used statistical clustering to group corrosively due to
environment and estimate the damage evolution based on long term expire parameters [H. Wang, et al,
Computer-Aided Civil and Infrastructure Engineering, May 2014]. The quantification of corrosion precursors
were used to estimate the effect of the environmental parameters in metallic and coated metallic structures,
the tropical environment can be characterized based on the same assumption. The environmental properties
will influence the damage evolution based on the seasonal characteristics, location and chemical composition
of the environment. The functional relationships will be used to develop the framework for the statistical and
probability functions.
Task 2 Laboratory scale characterization in wet-dry electrolytic laboratory environment conditions.
Hypothesis: Use the characterization method in previous phase’s to develop the transport mechanisms when
cycling environmental conditions exist in selected materials. Deterministic-probabilistic development can
correlate short term laboratory experiments for simulated corrosive wet-dry cycles in the tropical
environment.
Pre-Task 2: Laboratory test plan, development and analysis for cyclic wet conditions and framework for
theoretical deterministic-probabilistic modeling (12 months).
During this task of the project, laboratory design teams for the environmental exposure sites will actively
deploy, track and retrieve the samples in accordance with the procedures identified in task 1.
Using the understanding of Task 1, we will develop the theoretical and experimental procedure for selected
materials in laboratory cycling conditions, and then postulating damage evolution mechanisms. Laboratory
experiments will be used to validate the algorithm for the developed model. Task 2 consists of two sub-tasks
and lasts 12 months.
The model proposed in Task 1 and mechanisms will be used for laboratory conditions baseline system formed
by different prototypes, such as metallic, coated metallic and nonmetallic materials exposed in tropical
environments. Nine selected materials will be exposed in fog chamber conditions, a total of 10 samples per
material will be evaluated in laboratory conditions. The testing will include the characterization,
quantification and analysis of laboratory environment.
The objective in this phase is to experimentally characterize and quantify the critical parameters affecting the
damage mechanisms and how they correlate during wet-dry conditions. We will achieve this task in the
environmental fog chamber conditions for each material with the information on the mechanisms and
modeling proposed in Task 1. We will include the findings of the cycling water by the environmental chamber.
Although the suitability of the model framework will be evaluated as we learn the damage mechanisms in Task
2, we do not plan to devote substantial resources to this task. Rather, we will seek to develop a very general
approach in both sub tasks that can be used for a variety of deterministic/probability equations of this general
class.
Task 2.1 Comprehensive characterizations for transport and interfacial mechanisms in we-dry electrolytic
conditions for metallic, coated metallic and nonmetallic materials.
Modeling for wet-dry conditions for the corrosive environment will follow methodology for natural tropical
immersion developed in Task 1. The approach used for the development of transport and degradation
mechanisms is to develop functional expressions and/or probability functions of the cyclic wet-dry electrolyte.
The metallic, coated metallic and non-metallic materials will create different damage mechanisms interface
between the environment and the solid state system. The experimental conditions will include fog spray
chamber and the high use of resolution surface techniques to account for the effect and influence of the
cycling conditions at each environment/surface interface. We will quantify the damage for each material at
different time intervals during the dry period and/or in the environmental chamber conditions. The use of
high resolution techniques, such as LEIS, SEM, AFM< IFM, and SCEM will be used to identify, characterize and
quantify physical parameters that will relate the transport and interfacial (corrosion) mechanisms for the
prototypes models. Several samples (nine different materials in duplicates as different exposure times) will be
used to account for the damage evolution for the high resolution characterization during the fog chamber
conditions.
The previous task involved the spatial transport within the solid state formed by the organic coating; the
inorganic coating and the substrate consider different transport mechanisms and chemical/electrochemical
damage processes. Most of the previous work reported for organic coatings relates to the water uptake, and
the damage of metallic structures that considers stochastic and random distribution of damage due to
localized attack (pitting), both quantification has been done by using simple semi-empirical expressions with
no consideration of corrosive precursor vs. performance. By using control environment and sample
measurements/characterization, the quantification of damage mechanisms will be conducted by correlating
the physical properties for the samples within the state of the damage and the effect of the environment.
High resolution surface techniques will characterize the spatial distribution of the damage due to
environmental exposure at each material. The unification of probabilistic and deterministic modeling will be
based on the quantification and characterization of phenomenological parameters, such as surface damage,
potential profile, corrosion products (for metallic samples), capacitance or impedance (for coated metallic
samples) with inherit parameters of the system, such as crystalline structure, hydrophobicity, chemical
content (binders and pigments) to improve the rationalization of theoretical-performance properties.
Previously we used statistical clustering to group corrosively due to the environment and estimate the damage
evolution based on short term experiments [Hui Wang et al Journal of Structural Safety May 2014]. The
quantification of corrosion precursors were used to estimate the effect of environmental parameters in
metallic and coated metallic structures, the tropical environment can be characterized based on the same
assumption. The laboratory conditions properties will influence the damage evolution based on the
environment characteristics, location and chemical composition of the environment. The functional
relationships will be used to develop the framework for the statistical and probability functions. NCERCAMP
staff will begin the analysis process as soon as photographs, data and samples are retrieved. This will be a
continuous process beginning in month three of the project with a total of eight exposure cycles. Thus, a
preliminary report of findings will be delivered at the end of the fourth cycle (approximately month 15 of the
project). Analysis will continue through the final exposure period and a final report will be generated at the
end of the period of performance.
The final report will include the following: an analysis of the data from each respective test site, a comparative
assessment of the results with the finding of the ARO reports, findings of the value added of environmental
exposure as a supplement to laboratory testing and recommendations for the integration of these activities
into future DoD acquisition programs.
Product Deliverables:
•
•
A database for atmospheric corrosion or degradation for key material in tropical environments.
A framework to elucidate, quantify and characterize mechanisms of degradation for metallic, coated
metallic and nonmetallic materials.
• A framework to establish corrosivity for atmospheric conditions in a dynamic Map in Panama locations.
• A framework for deterministic/probabilistic modeling for atmospheric corrosivity and degradation.
• The publication of findings in technical quarterly and final report.
• The publication of 1 conference paper and 1 journal article per year.
• Presentations for annual DoD corrosion conference and TCC meetings.
• A Ph.D. student who will work in a highly interdisciplinary area.
• Quarterly Quads charts.
Relevance and Cost of Corrosion Relationship:
Relevance for this research includes more reliable evaluation of coating systems service and enhances
performance assessment and life prediction. Also, the goal of the proposed work is to contribute methods or
technologies used as monitoring or risk management tools of DoD assets. The definition and quantitative
descriptions of damage evolution (shape and depth of corrosion) and the reliability models with different
failure modes will be used for the corrosion assessment, structural analysis, and risk management for
maintenance and repairing programs.
The impact of corrosion on the safety, affordability, and sustainability of US Air Force assets is a long-standing
concern within the Department of Defense. While the absolute magnitude of the corrosion problem might
not be accurately quantified, recent studies have shown significant progress on estimating corrosion-related
costs and evaluating availability impacts. In order to maintain a desired level of US Air Force assets exposed to
corrosion, there is a need to further understand the performance of the corrosion-impacted coating system
used in the US Air Force.
Budget Summary and Timeline Schedule
The project is proposed as a 36 month project. The total cost is $296,767.00 USD.
Budget Justification
Personnel
Senior Personnel
The University of Akron has assembled a unique and creative team to perform this research. Ms. Sue Louscher
will serve as the Principle Investigator and Dr. Homero Castaneda-Lopes will serve as Co-Pi. Dr. Summer salary
of support is requested each year of the project. Dr. Castaneda-Lopez will track budgets and schedules, lead
the preparation of reports, and ensure frequent formal and informal communication among team members.
He is the originator of the damage evolution stages concept, and his expertise is in the areas of
electrochemistry, materials, and corrosion, with a focus on elucidating the environmental effects of metallic
chemical degradation and interfacial mechanisms on electrochemical systems. He has 14 years of experience
using electrochemical techniques to monitor interfacial phenomena in materials for the power,
environmental, military, and energy industries. He received academic awards for best thesis and graduate
study achievement, as well as a government scholarship for doctorate studies at Penn State University. Dr.
Castaneda-Lopez holds for patents in electrochemical and corrosion-related areas and more than 55 peerreviewed and conference presentation publications.
Ms. Sue Louscher, Executive Director of NCERCAMP, will provide coordination and integration activities for
this project. She will be the primary liaison with the government partners and the on-site contractors at the
exposure facility.
Senior personnel salaries are calculated based upon standard university rates for those individuals. Salaries
are incremented by 4%/year in years two-four. Contract professionals are incremented by 3%/year.
Other Personnel
One equivalent PhD level graduate assistant is required in each year of the project. Also a Postdoctoral fellow
is required for 16 months. The graduate assistant will have materials science engineering background and
experimental skills are required for simulation of the damage evolution. The postdoctoral fellow will have
statistics and probability background with strong knowledge of damage evolution of coated and non-coated
metallic substrate. The graduate assistant will develop theoretical/experimental model. The graduate
research assistants will be supported by calendar year appointments; full time effort for these appointments is
defined as 20 hours/week. Salaries are incremented by 3%/year.
Fringe Benefits
Effective July 1, 2014, fringe benefits at The University of Akron are calculated according to a pooled rate,
which varies by type of appointment. For the Personnel proposed on this project, the rates are as follows:
Faculty Summer- 17.3% year one, increasing by .6%. Contract professionals- 31.4% year 1 increasing by .6% in
succeeding years.
Post-doctoral
associates- 42.7%/year.
Graduate and
undergrad student hourly assistants- 3.1%/year.
Travel/Foreign
The principle investigator and Co-Pi will travel to Panama facilities three times during the 36 months of the
project. Support for three/four day trips twice in each year are requested for Dr. Castaneda and Sue Louscher.
The estimated cost of $5000/year includes ground transportation, meals and lodging. Dr. Castaneda and Sue
Louscher will present the results, have meetings with the team and give the updates to the AFRL personnel.
All requested travel will be in compliance with sponsor and institutional policies.
Travel/Domestic
The principle investigator will travel to DoD TCC meetings and either NACE of ECS conferences in all three
years of the project. Support for two/three day trips in each year are requested for Dr. Castaneda and one
PhD student. The estimated cost of $1500/year includes air/ground transportation, meals and lodging.
Other Direct Costs
Materials and Supplies.
None.
Other
The University of Dayton Research Institute will provide the coatings application for the system prototypes at
a cost of $6000/year for two years. The cost was estimated by previous quotation for different coating
applications including 80 samples and the cost being $6000.00.
Machine
time
is
requested @ $3000/year in years 1 and 2.
Indirect Costs
Facilities and administrative (indirect) costs are calculated at 50.0% MTDC, per the University’s current
federally negotiated rate agreement (DHHS dated 11/30/2011).
Project Title: Inert Atmospheric Plasma Polymerization (IAP) for Improved Corrosion Protection
Principle Investigator: Ali Dhinojwala and Mark Foster
Work Statement:
The main objective is to quantify the chemical and structural natures of IAP films, comparing them to those of
coatings formed by vacuum processes as well as current conventional coating processes with the intent to
optimize a process for formation of outstanding adhesion promotion layers by an IAP process. We will test the
hypothesis that surface modifying plasma polymerized coatings made using IAP substantially enhance the
adhesion and corrosion protection provided by polymeric coatings on aluminum substrates without the use of
VOCs. We will specifically quantify the adhesion to metal and compare performance in outdoor tests with
conventional coating systems. This will establish the validity of this process as an alternative solution for
corrosion protection. The outcome of this work would be important for optimizing the conditions for
continuous IAP processes necessary for large-scale production of plasma coated parts for DoD use.
The proposed approach will leverage equipment and expertise acquired with other funding. Two DURIP
grants have provided equipment in Foster’s lab and expertise in the characterization of plasma-polymerized
films was developed in Foster’s group [7-10] under past Air Force funding on plasma enhanced PECVD films for
photonics. Dhinojwala’s research group has successfully aligned carbon nanotubes to create steam and icephobic substrates. In addition, Dhinojwala is currently collaborating with a local company to develop a
continuous IAP process. Also, both Foster’s and Dhinojwala’s groups have extensive experience in the study of
thin films and interfaces with a wide array of experimental tools. Collaboration with ARL brings EIS
characterization, expertise in corrosion testing, and world-class capabilities in deposition on large substrates,
and expertise and knowledge of the coatings specifications for DoD. The University of Hawaii collaboration
provides unique environmental testing capabilities well known to the TCC.
a. Substrates: Aluminum and model AA2024 aluminum alloy films will be made using DC magnetron
sputtering at the NanoFab at the National Institute of Standards and Technology, where Foster’s
group has successfully deposited films of various microroughnesses from AL and AA2024 targets by
controlling the rate of sputtering. The Native oxide will form immediately upon removal from the
deposition system. Dhinojwala [11] and Foster [12-13] have already studied water at the interface
between polymer coatings and such well-defined metal oxide/metal thin film substrates.
b. Chemistry of Coatings: Films will be deposited from hexamethyldisiloxane (HDMSO) or maleic
anhydride (MA)or epoxies (glycidyl methacrylate or allyl glycidyl ether), initially, using both
processing environments, then the structures and properties of those films made in a vacuum and
at atmospheric pressure characterized using various techniques and compared. The Dhinojwala
research group has extensive experience working with these monomers. Perhaps most promising
will be films with gradient structures which can be deposited by beginning the deposition with one
monomer and then moving through mixed feed streams of various compositions of a second
monomer.
c. Plasma Process: Plasma enhanced vapor deposition of thin films from precursors will be carried out
in an inductively coupled, electrode-less vacuum plasma unit operated at 13.56 MHz frequency and
in an atmospheric plasma unit operated on the principle of dielectric barrier discharge. The
monomers will be vaporized or sublimed under vacuum by controlling their partial vapor pressures.
The monomers will be nebulized to form a carrier gas to control surface oxidation. Relative vapor
pressures of the monomers, carrier gas flow rate, plasma power, reaction time and continuous v/s
pulsed mode of plasma will be used as process control variables and their effect on morphology
and surface chemistry of the deposited coating studied.
d. Spectroscopic Characterization: Film surface chemistry will be quantified with XPS and variation
with depth determined using etching combined with XPS. Overall chemical composition of the
films will be studied with IR and Raman spectroscopies and the chemistry at the interface between
plasma coating and metal oxide sensitively probed with infrared-visible sum frequency generation
spectroscopy [14-15].
e. Coating Uniformity: Surface microroughness, film uniformity and variation in morphology with
depth will be quantified using XR in Foster’s lad and NR at NIST or Oak Ridge National Laboratory
[7-10]. The techniques are complementary. Variations in density and composition not readily
separated with just XR or NR will be sorted out with matched measurements with both. NR
measurements of films swollen with a good solvent [8-9] will provide the depth profile of relative
cross-link density. AFM will provide complementary characterization of lateral uniformity of the
surface morphology, and variation of surface microroughness with processing parameters.
f. Adhesion Testing: Adhesion of the coatings to the substrate will be tested at UA using a pull-off
method or a tape test (ASTM D3359). The adhesion with the overlaid coatings will be tested using
Johnson-Kendall-Roberts (JKR) measurements. Dhinojwala’s research group has extensive
experience using this technique to study adhesion of PDMS lenses in contact with polymer-coated
substrates [14-15].
g. Corrosion Testing: Aluminum coupons with coatings incorporating the plasma deposited adhesion
layer will be tested using EIS (ARL) and compared in outdoor tests in Hawaii (U. Hawaii) with
coupons protected with currently accepted coatings.
h. Collaborative Work using the Plasma Instrumentation at ARL Laboratory: At ARL there is an
ongoing effort to use the micro-jet deposition with atmospheric plasma to coat large metal pieces
or continuously coat fabric using roll-to-roll processing.
Product Deliverables:
The main deliverables will be the quantification of the chemical quality structure of IAP films, comparing them
with films deposited by conventional PECVD and linking that chemical quality and structure to enhancement
of corrosion protection by enhancement of adhesion as compared to that in current coatings. To capitalize on
the promise of IAP films their structure must be better understood. Comparison with currently accepted
coatings will validate performance advantage.
Relevance and Cost of Corrosion Relationship:
The use of IAP to enhance adhesion promises lower cost application, combination of surface cleaning with
deposition, better film uniformity, and elimination of VOCs. The technique has been demonstrated to be
scalable. An understanding of how to optimize corrosion protection through the optimization of adhesion by
varying process parameters would enable break-through progress in corrosion protection.
Project Title: A Collaborative Agreement between The University of Akron and U.S. Military Academy at West
Point to Develop and Verify Localized Corrosion
Principle Investigator: Gerald Young, C. Clemons, K. Kreider, N. Mimoto
Work Statement:
The objective of this work is to further develop a basic methodology for a probabilistic analysis tool to assist
with pitting corrosion risk management of equipment/infrastructure that is subject to dynamic corrosive
degradation processes and mitigation schemes. The work is a collaborative effort between The University of
Akron (UA) and The United States Military Academy (USMA). Preliminary Markov models have been
previously developed at UA to estimate pitting damage accumulation density distributions on a metal surface,
as a function of input parameters for pit nucleation and growth rates. The input parameters are currently
selected by calibrating model outputs with laboratory or field data sets from the literature.
The Markov models have been solved using both analytical and numerical techniques. The analytical solutions
are valid under some restrictive assumptions on the input parameters. These analytical solutions have been
incorporated into preliminary versions of cdf (computable document format) stand-alone tool driven by
Mathematical software.
To advance this existing methodology for estimating pitting damage accumulation, the goals of this proposal
are to
1. Develop Mathematical code to implement the numerical simulation of the Markov models into a cdf
(joint effort between USMA and UA). The result will be an enhanced cdf that will allow the input
parameters to be time dependent, needed to stimulate dynamic changes in environmental and
operating conditions.
2. Identify Army entities that collect pitting corrosion information, such as pit density vs. time and pit
density vs. depth over time, and used this pitting corrosion data to develop guidelines for selecting
input parameters for the pit nucleation and growth rates needed by the cdf developed in goal 1 (joint
effort with USMA taking the lead). Here the intent is to find benchmark expressions for the inputs
from data, such that there are expressions for high salinity environments, high humidity environments,
etc., so that model input is consistent with DoD applications.
3. Develop next generation Markov models that include additional scientific features, such as metastable
pits (UA effort). Here the intent is to derive expressions for the inputs needed by the cdf developed in
goal 1.
4. Develop an easy to use tool for military planners to compare courses of action based on the impacts of
pitting corrosion in dynamic environmental conditions (joint effort with USMA taking the lead). This
initial tool will be small in scale with a small number of materials in a small number of environments.
This tool will provide a framework that can easily be expanded to more material and more
environments when additional data becomes available. A protocol for modification to include further
data sets will be outlined.
Product Deliverables:
In the procurement phase, a procurement team will be able to use this analysis tool to predict the risk
levels of pitting corrosion on new vehicles in different theaters of operation without the additional costs of
any computer software and very little additional training. This tool will allow decision makers to use
pitting corrosion risk as a criterion to distinguish between multiple courses of action during vehicle
procurement or allow quick feedback to the procurement team to request a design change to high pitting
corrosion risk areas of a vehicle before the corrosion problem even occurs.
In the equipment management phase, the analysis tool will allow equipment management decision
makers to more effectively plan their corrosion mitigation at the equipment (vehicle, infrastructure, or
other equipment) level instead of the current method of broad rules of thumb that are much less
economically effective. The analysis tool will make a pitting corrosion prediction based on the conditions
of the operating environment, which is especially useful when equipment is scheduled to be used in more
than one operational environment, allowing for more effective corrosion risk management. Equipment at
all locations will not be treated the same, so equipment in higher corrosive environments will be able to
have a more specialized maintenance plan to mitigate the effects of corrosion.
An additional benefit of this project is the partnership between the University of Akron and the United
States Military Academy. This partnership will allow a greater appreciation and base of knowledge for the
Army’s future leaders, because this project will help the process of bringing more cadets and military
officers into the corrosion discussion. These leaders will bring their corrosion knowledge with them as
they command units and train their soldiers to reduce the effects of corrosion throughout the operational
Army and the Army Corps of Engineers.
Finally, the continuing research efforts in corrosion at UA serve to bring more graduates with expertise in
corrosion modeling and risk assessment into the workforce.
Relevance and Cost of Corrosion Relationship:
We are requesting Y15 funds to accomplish the project’s goals from September, 2014 through September
30, 2015. If the project team is able to move forward into further testing at field locations, further funding
may be requested on a case by case basis with approval through OSD.
Summer support is requested for this project’s graduate assistant. USMA plans to support any cadets
through its Academic Individual Advanced Development (AIAD).
UA travel consists of approximately $4,850 for four faculty to travel to the USMA at West Point, $4,450 for
four faculty to travel to DoD and Allied Nations Corrosion Conference in August 2015, and $2,000 for one
faculty member to travel to another (to be determined) conference. Each trip assumes three nights stay in
a hotel ($500), per diem ($71), airfare ($350), car rental ($400), registration fees ($300), and parking, etc.
Project Title: Development of a Numerical Framework for Prediction of Hydrogen-Induced Stress-Corrosion
Cracking
Principle Investigator: Xiaosheng Gao, Erik Knudsen, Stephen M. Graham
Work Statement:
The objective of the proposed work is to develop a numerical tool that can be used to predict hydrogeninduced stress-corrosion cracking (HISCC) in engineering components and structures. The numerical model
includes simulations of two interactive processes: the hydrogen diffusion simulation to determine the local
hydrogen concentration and the damage and fracture simulation to account for the influence of hydrogen on
plasticity and ductility. The numerical model will not only help us gain a better understanding of the
chemical and mechanical processes and their interaction involved in HISCC but also will help us get a step
closer to the long term goal, to replace expensive and time-consuming experimental programs by numerical
simulations. The proposed research will be a joint collaboration between the University of Akron, the United
States Naval Academy, and the Naval Research Laboratory, where a blend of experimental testing,
theoretical modeling and numerical simulation work will be conducted.
Background: Stress corrosion cracking or, more generally, environmentally assisted cracking is a major cause
for failure of engineering components and structures [1]. One of the mechanisms leading to environmentally
assisted cracking is the embrittlement of the material due to the uptake of atomic hydrogen from the
environment. Hydrogen induced cracking occurs when a critical combination of local hydrogen content,
stress, strain and sensitivity of the microstructure to hydrogen degradation is reached. Various mechanisms,
such as hydrogen enhanced localized plasticity (HELP) [2] and hydrogen enhanced decohesion (HEDE) [3],
contribute to hydrogen induced cracking. To model HISCC, both hydrogen diffusion simulation and material
damage and fracture simulation need to be conducted. Hydrogen dissolved in metals resides either at normal
interstitial lattice sites (NILS) or reversible trapping sites at microstructural defects generated by plastic
straining such as dislocations. One important fact is that hydrogen transport is affected by hydrostatic stress
and plastic strain, thus hydrogen transport equations are fully coupled with the elastic-plastic deformation.
Atomic hydrogen increases the mobility of dislocations, leading to a localization of the plastic deformation,
which has been observed in high-strength aluminum alloys, steels, pure nickel, pure iron, and α-titanium at
high stress intensities where the crack propagates faster than the rate of hydride formation in the fracture
process zone. In addition, the presence of hydrogen reduces the material’s ductility as a result of hydrogen
embrittlement. All these need to be considered in the HISCC simulation.
This project intends to develop a numerical framework that can be used to predict HISCC in engineering
components and structures. DoD sponsored projects conducted by the investigators previously, in
collaboration with Naval Warfare Center Carderock Division, Bettis Atomic Power Lab and Naval Research
Lab, have developed plasticity and ductile fracture models for a number of materials in air, such as AA 5083H116, commercially pure titanium, DH36 steel, Nitronic 40 stainless steel, and β-treated Zircaloy. We have
shown that the widely adopted classical J2 plasticity theory does not correctly describe the plastic response of
many of these materials [4] and the ductile failure process of these materials depends strongly on the local
stress state [5]. Consequently we have developed a plasticity model that involves all three stress invariants and
a ductile fracture model that accounts for the effects of both the stress triaxiality and the Lode parameter [610]. To simulate HISCC, these models need to be modified to include the dependence on local hydrogen
concentration. In the proposed project, the DH36 steel, which is widely used in marine structures, will be used
in model development. Future studies will extend the model to other materials of the interest to the DoD. The
proposed effort is summarized as follows:
1. Task 1 – Develop a Numerical Model to Simulate the Hydrogen Transport Process
Assuming that hydrogen diffusion occurs through transposition between interstitial sites within the
lattice and that the transported hydrogen resides at the interstitial sites or at the trapping sites,
Sofronis and McMeeking [11] derived an enhanced diffusion equation and Krom et al. [12]
introduced an additional term to account for the plastic strain rate dependence where ∂/∂t

represents the time derivative, NT represents the trap density, θT represents the occupancy of the
trapping sites, CL represents the hydrogen concentration in normal interstitial lattice sites (NILS),
CT represents the hydrogen concentration in trapping sites, DL represents the hydrogen diffusion
constant through NILS, VH is the partial molar volume of hydrogen in solid solution, R is the gas
constant, T is the absolute temperature, is the plastic strain.
The above governing equation for transient hydrogen diffusion is coupled with mechanical
quantities such as hydrostatic stress, plastic strain and strain rate and will be implemented in a
commercial finite element code, ABAQUS, via a user supplied subroutine. ABAQUS does not
provide a user interface for mass diffusion except for solving the Fick’s equation, which is not
sufficient for the current problem. Fortunately ABAQUS does provide a built-in program for
heat transfer analysis and allows the user to define the thermal behavior of the material for
transient heat transfer analysis via a user subroutine UMATHT. The analogous structure of the
Fourier’s equation of thermal conduction and the diffusion equation make it possible to
implement the hydrogen diffusion model in ABAQUS, where a UMATHT subroutine can be
used to match variables of the governing equations for heat transfer analysis with those for
hydrogen diffusion.
To validate the user subroutine for hydrogen diffusion simulation, problems solved by Sofronis
and co-workers [13] using their in-house code will be re-visited and the simulated results will
be compared with their published ones.
2. Task 2 – Incorporate the Dependence of Hydrogen Concentration in the Plasticity Model
The plasticity model developed for the material tested in air will be extended to include the
effect of hydrogen enhanced localized plasticity (HELP), where the hardening will be made
dependent on the hydrogen concentration. For example, Sofronis et al. account for the
softening effect due to HELP by modifying the flow curve as σ𝑦𝑦(𝜀𝜀𝑝𝑝, 𝑐𝑐) = 𝑓𝑓(𝑐𝑐)σ𝑦𝑦(𝜀𝜀𝑝𝑝), where σ h
is the uniaxial flow curve under the influence of hydrogen, σ a is the flow curve in air, and f(c)
is a function of the hydrogen concentration. The model will be implemented in ABAQUS via a
user defined subroutine UMAT and calibrated by using experimental data obtained from
tensile tests on hydrogen charged specimens (described in Task 4).
3. Task 3 – Incorporate the Dependence of Hydrogen Concentration in the Damage Model
The damage model developed for the material tested in air will be extended to include the
reduction in ductility resulted from hydrogen embrittlement. This will be done by scaling the
failure strain by a factor dependent on the hydrogen concentration, i.e., 𝜀𝜀 𝑓𝑓(𝜂𝜂, 𝜉𝜉, 𝑐𝑐) = 𝑔𝑔(𝑐𝑐) 𝜀𝜀𝑎𝑎
(𝜂𝜂, 𝜉𝜉), where 𝜀𝜀ℎ represents the failure strain with the presence of hydrogen, 𝜀𝜀𝑎𝑎 represents
the failure strain in air, η represents the stress triaxiality, ξ represents the Lode parameter, and
𝑔𝑔(𝑐𝑐) is a function of the hydrogen concentration. A continuum damage mechanics approach [9,
15] will be adopted, where a damage parameter will be defined in terms of the accumulative
plastic strain as a function of the stress triaxiality, the Lode angle and the hydrogen
concentration. The model will be implemented in the ABAQUS UMAT and calibrated using data
from the Task 4 experiments.
4. Task 4 – Conduct Experiments to Obtain Data for Model Calibration and Verification
Uniaxial tensile tests and combined tensile plus torsion tests will be conducted on hydrogen
charged specimens to calibrate the plasticity model from Task 2 and the damage model from
Task 3. These tests will be conducted using specimens electrolytically charged with hydrogen by
cathodic polarization in in an aqueous solution containing a recombination “poison” to inhibit
formation of molecular hydrogen during the evolution reaction, and thereby accelerate the
absorption of hydrogen into the metal. The absorption rate will be controlled by changing the
applied current density, solution, and/or “poison” to achieve the desired hydrogen content.
The model developed in Task 1 will be used to determine the local hydrogen concentration in
the specimen and some samples will be sent out for measurement of hydrogen content to
check the model predictions. The time between charging and testing will be kept to a
minimum in order to prevent desorption of internal hydrogen. The plasticity model will be
calibrated using smooth tensile and pure torsion tests, while the damage model will be
calibrated using notched flat and round tensile tests and combined tension plus torsion tests
to create different states of hydrostatic stress, triaxiality and Lode angle at failure. Model
calibration will be conducted by adjusting model parameters so that model predictions
provide a best match to experimental data. This is the same approach that was used in
previous work mentioned in the background except that here an additional variable of
hydrogen content will be introduced.
5. Task 5 – Validate the Plasticity and Damage Model
Once the plasticity and damage models are calibrated, they will be applied to predict HISCC
crack growth tests conducted at different loading rates for model verification. The tests will be
performed following the ASTM Incremental Step Loading Technique in standard E1624 using
standard C (T) specimens immersed in an aqueous solution with applied potential to promote
hydrogen absorption. The step loading profile will be varied to investigate rate effects on
hydrogen assisted crack growth. The effect of stress state will also be investigated by testing
specimens that are notched only and pre-cracked.
6. Task 6 – Student Involvement
This project will be a joint effort between Prof. Stephen Graham at the US Naval Academy and
Prof. Xiaosheng Gao at the University of Akron. Dr. Erik Knudsen at the Naval Research
Laboratory will also actively participate in this research. An important task of the project is to
educate and train students and get them involved in this project. At UA, one graduate student and
one undergraduate student will participate in this project. At USNA, the project will involve one
or more undergraduate students performing cathodic charging and conducting tests. In addition,
students at University of Akron and Naval Academy may spend time at Naval Research
Laboratory with Dr. Erik Knudsen to conduct stress corrosion cracking experiments. All these
training efforts will teach our future engineers, scientists and naval officers about potential
corrosion-assisted cracking mechanisms so that they have a better understanding of
civilian/military systems and can make better-informed decisions.
Relationship to the previous work:
The proposed work is related to our ongoing research supported by ONR and DoD TCC program
to develop plasticity and ductile damage models for CP titanium. It is also related to our previous
ONR and NAVSEA funded research for developing plasticity and ductile fracture models for
reliability assessment of ship structures, where DH 36 steel and AA 5083-H116 were studied.
Future work:
Our long-term goal is to develop a theoretical, experimental and numerical framework that can
be applied to model the plasticity and ductile fracture behavior of advanced engineering
materials and to develop a numerical tool that can predict environmentally assisted crack
propagation in engineering structures and components. Thus the future work will be to further
refine the models developed in this study and to extend them to other materials of interest to
the DoD.
Product Deliverables:
The quarterly quad charts, final report, and additional publications, documents and data will
be submitted through the Engineering Resource Data Management (ERDM) online system. A
list of deliverables are summarized as follows
a. Quarterly quad charts summarizing research progress.
b. A final report containing detailed descriptions of the models developed in this
study, finite element implementation of the models, experimental procedure
and experimental data, model calibration process, and comparison between
model predictions and experimental results.
c. Source code of the user subroutines to implement the models developed into
ABAQUS.
d. Transfer of knowledge to DOD collaborators to assist in their development of
algorithms and software tools.
e. Report(s) from Independent Research projects by one or more undergraduate
students at the United States Naval Academy.
f. Papers, articles and dissertations resulting from the project.
g. Experimental data and microscopy images generated in this research.
h. Presentations at annual DOD Corrosion Conference and TCC review meetings.
Relevance and Cost of Corrosion Relationships:
Potential Impact/Benefit: Structural damage (i.e. cracks) in military structures can manifest itself
in several ways. For example, during the fabrication/forming process structures can be stressed
to the point where some ductile damage has occurred. The component in question may also be
subjected to additional loading (corrosive environment, fatigue, shock, high temperature, etc.)
during operation which further extends the crack over the service life. Computationally based life
predictions would enable structural analysts and fleet maintenance personnel to establish suitable
inspection intervals and/or determine when a part should be replaced before a critical condition is
reached without having to rely on expensive testing done on full-scale builds. The outcome of
this study will provide the DoD a numerical tool for damage assessment and life prediction of
structures and components subjected to corrosive environment.
Potential Customer: A wide variety of U.S. military platforms and structures are exposed to
marine environments where environmentally assisted cracking is a concern. The Naval Research
Laboratory and the United States Naval Academy frequently collaborate with many of the Naval
Warfare Centers to address the issues pertaining to damaged (or cracked) structures in marine
environments. This computational tool could be utilized by a number of scientists and structural
engineers who need to make decisions that are critically important from an operational and/or
fleet maintenance standpoint. Although the proposed research is in collaboration with several
technical arms of the U.S. Navy, the results of this research can be applied to military structures
operated by other military branches.
The proposed research will be conducted in three years: we will carry out tasks 1, 4 and 6 in
FY15, tasks 2, 3, 4 and 6 in FY16, and tasks 5 and 6 in FY17. It will be a collaborative effort
between Prof. Stephen Graham at the US Naval Academy, Dr. Erik Knudsen at Naval Research
Laboratory and Prof. Xiaosheng Gao at the University of Akron. The experimental work will be
carried out at USNA and NRL, while the model development, implementation and finite element
analysis work will be mainly carried out by the University of Akron.
Dr. Gao will devote one summer month per year and Dr. Graham will devote two summer
months per year to conduct the proposed research and advise, mentor, and oversee the
undergraduate and/or graduate students’ work. During the academic year, both Dr. Gao and Dr.
Graham will actively involve in the research and advise and oversee the students’ efforts on the
project.
The combined total budget for UA and USNA is $316,333 for three years ($113,264 for FY15,
$100,588 for FY16 and $102,481 for FY17).