Investigation of Organic Coatings Durability
on Concrete Reinforcement Corrosion Protection
with the Synergistic Influence
of Corrosion Inhibitors
S.Kalogeropoulou1, P.Pantazopoulou1, Th.Zafeiropoulou2, K. Sideris3
1. Electrical Engineering Department, Technological Educational Institute of Piraeus, Athens, Greece
2. Faculty of Chemical Engineering, National Technical University of Athens, Greece
3. Democritus University of Thrace, Dept. of Civil Engineering, Xanthi, Greece
eRA – 9, T.E.I. of Piraeus, 22-24 September 2014
In this work the results obtained until now in the
framework of an ARCHIMEDES III research project
entitled "Investigation of Organic Coatings
Durability on Concrete Reinforcement Corrosion
Protection with the Synergistic Influence of
Corrosion Inhibitors” are presented.
22/9/2014
eRA-9
2
Aim of the study
The action of various organic coatings and corrosion
inhibitors in the protection of steel reinforcement in highly
corrosive conditions is investigated.
Five different types of organic protective coatings have
been chosen to be studied: a two-pack epoxy paint, a twopack polyurethane paint, a nanotechnology paint and two
acrylic dispersions.
A classification of the protective action of the organic
coatings against corrosion, based on the results of various
experimental methods, is presented.
22/9/2014
eRA-9
3
Reinforcement corrosion – Protection methods
Reinforcement corrosion: main cause of reduction
of a structure’s life
coatings on the surface of concrete
available corrosion inhibitors
protection cathodic protection
methods stainless steel reinforcement
coating of reinforcement
22/9/2014
eRA-9
4
Organic coatings
Surface coatings on concrete:
 prevent the deterioration by creating a physical
barrier between the concrete structure and the
harmful substances from the environment
 improve or maintain the appearance
 offer an effective and reliable solution for the
protection both of the concrete and the
embedded steel
22/9/2014
eRA-9
5
Desired properties of organic coatings




Good adhesion to concrete even when wet
Resistance to high alkalinity of concrete
Ability to penetrate into the pores and cracks of concrete
Good resistance to ultraviolet (UV) radiation and
weathering
 Good mechanical strength
 Prevent entry of water but allow water vapor permeation
 High resistance to the permeation of sulfur dioxide and
carbon dioxide and to the penetration of chloride ions in
the pores and cracks (less than 0,3 mm) of the concrete
22/9/2014
eRA-9
6
Corrosion inhibitors
Corrosion inhibitors have been successfully used as
admixtures to concrete to reduce the risk of reinforcement
corrosion.
Alkanolamine-based corrosion inhibitors
 move through the pore structure of concrete to reach
the surface of reinforcing steel, where they form a
protective film
 reduce chloride ion ingress into concrete
 are classified as mixed inhibitors, because they influence
both the cathodic and the anodic process of corrosion
22/9/2014
eRA-9
7
Degradation of coatings
Μain factors influencing the durability of coatings:
 sunlight (ultraviolet radiation)
 moisture
 heat
Τhe result of the combination of these factors is much
more serious than each factor individually.
Degradation can vary from mere surface discoloration
affecting the aesthetic appeal of a product to substantial
loss of mechanical properties.
22/9/2014
eRA-9
8
Properties studied and methods used
 Reinforcement’s corrosion behavior
 Effect of UV-radiation to coatings
 Liquid water and water vapor transmission rates
 Carbonation depth
22/9/2014
eRA-9
9
Reinforcement’s corrosion behavior
 Use of the Strain Gauge (SG) technique, which is based
on the appearance of swelling strain near the steel
reinforcement in the concrete and is measured by
embedded SG sensors in mortar specimens. The cause of
the swelling tension is the formation of corrosion products
(iron oxides, Fe3O4, Fe2O3, FeO(OH)) having greater specific
volume than iron.
 Determination of the gravimetric mass loss of
reinforcing steel bars after a certain period of exposure in
the corrosive environment. Mass loss (according to ISO/DIS
8407) is estimated as the difference between the initial and
the final mass of the bars, as determined by removing the
corrosion products from the bars.
22/9/2014
eRA-9
10
Effect of UltraViolet-radiation to coatings
 Dry Film Thickness was measured according to ASTM
D4138 “Standard Practices for Measurement of Dry Film
Thickness of Protective Coating Systems by Destructive,
Cross-Sectioning Means”.
 Cross cut test was performed according to ISO
2409:1992(E) “Paints and varnishes – Cross cut test” and
ASTM D3330 / D3330M - 04(2010) “Standard Test Method
for Peel Adhesion of Pressure-Sensitive Tape”.
 In coated specimens coatings’ adhesion was measured
according to BS EN 24624:1993/ BS EN ISO 4624:2003
“Paints and varnishes - Pull off test for adhesion” and ASTM
D4541 - 09e1 “Standard Test Method for Pull-Off Strength of
Coatings Using Portable Adhesion Testers”.
22/9/2014
eRA-9
11
Liquid water and water vapor transmission rates
 Liquid water transmission rate of each coating is
determined according to standard DIN EN 1062-3:2008-04
“Paints and varnishes - Coating materials and coating
systems for exterior masonry and concrete - Part 3:
Determination of liquid water permeability”.
 Water vapor transmission rate is determined according
to standard DIN EN ISO 7783-2 “Coating materials and
coating systems for exterior masonry and concrete - Part 2:
Determination
and
classification
of
water-vapor
transmission rate (permeability)”.
22/9/2014
eRA-9
12
Carbonation depth
Measurements of carbonation depth are performed
according to BS EN 13295:2004 "Products and systems for
the protection and repair of concrete structures - Test
methods - Determination of resistance to carbonation" and
BS EN 14630:2006 "Products and systems for the protection
and repair of concrete structures - Test methods -
Determination of carbonation depth in hardened concrete
by the phenolphthalein method".
22/9/2014
eRA-9
13
Materials
standard proportions
cement : sand : water
Cement
CEM ΙΙ 32.5
Quarry sand
Coatings
1 : 3 : 0.5
Water
Inhibitor
Reinforcement
B500C
eRA-9
14
Chemical composition of Portland cement (%wt)
SiO2
Al2O3 Fe2O3 CaO MgO K2O Na2O SO3 CaO(f)
LOI
CEM II 32.5 20.67 4.99 3.18 63.60 2.73 0.37 0.29 2.41 2.41
2.52
Chemical composition of steel (%wt)
C
0.22
Mn
S
P
Si
1.24 0.044 0.032 0.28
22/9/2014
Ni
Cr
0.09
0.10
eRA-9
Cu
V
Mo
0.52 0.075 0.028
15
Organic Coatings Categories
 Two-pack epoxy coating (E)
 Two-pack polyurethane coating (P)
 Nanotechnology coating (N)
 Acrylic emulsion (A)
 Elastomeric acrylic dispersion (R)
 Uncoated specimens were used as reference (O)
22/9/2014
eRA-9
16
Coating procedure
The coating procedure for all coatings involves three
layers:
 The appropriate for each coating primer is applied on the
dried surface of the specimen, to achieve the best adhesion
between coating and mortar.
 24 hours
 The first layer of the organic coating is applied by brush.
 24 hours
 The second layer of the organic coating is applied by
brush perpendicularly to the first one.
 Coated mortar specimens are stored in the laboratory for
at least 7 days, so as coatings are dried and all quantity of
solvents has evaporated.
22/9/2014
eRA-9
17
Organic coatings - technical characteristics
S/N Code
1
2
3
4
5
Ε
Product
Color
Epoxy
Grey
Characteristics
Two-pack epoxy paint with amine hardener,
density 1,55 kg/Lt, spreading rate 6 m²/kg (100
μm), solids 95% w/v.
P Polyurethane Grey Two-pack polyurethane with aliphatic isocyanic
hardener, density 1,20-1,40 kg/Lt, spreading rate
9-11 m²/ Lt (50μm).
N
Paint for White Siloxane paint, density 1,60 kg/Lt, solids 50%
exterior use
w/v, spreading rate 8,6 m²/Lt.
A
Acrylic
White Acrylic dispersion, density 1.46±0.05 g/ml, solids
emulsion
61±2.5% w/w, pH 8.4±1, spreading rate 9±1
paint for
m²/Lt (2 coats).
exterior use
R Elastomeric White
Acrylic dispersion, undiluted for final coat,
insulating
density 1.35 g/ml, solids 60±2% w/w, spreading
acrylic paint
rate 2±1 m²/Lt.
22/9/2014
eRA-9
18
Primers – technical characteristics
S/N Code
Product
Color
Characteristics
1
ΕΑ Epoxy primer Colorless Two-pack epoxy primer, Α:Β-2:1 w/v with
(coatings 1-2)
hardener, solids 58% w/v, density 0,99
kg/Lt, spreading rate 10 m²/Lt.
2
ΑΑ Acrylic water- Colorless Density 1kg/Lt, solids 25,9% w/v, dilution
based primer
up to 1:4 with water, spreading rate 8-32
(coating 3)
m²/Lt.
3
SΑ
StyreneColorless Copolymers of styrene and acrylic resins,
acrylic primer
density 0.85 g/ml, solids 26±2% w/w,
(coatings 4-5)
spreading rate 7.5-8.5 m²/Lt.
22/9/2014
eRA-9
19
Conclusions A: Corrosion evaluation
 The protective action of all organic coatings against
corrosion of the embedded reinforcement is confirmed.
 Epoxy and polyurethane coatings present an exceptional
performance.
 The nanotechnology coating presents reduced protective
ability in accelerated corrosion conditions.
 For the system “corrosion inhibitor – organic coating” the
results have shown that their action is not added.
However there is an improvement of the protection
given by the coatings with the inhibitor presence,
especially in the case of the less effective coatings.
22/9/2014
eRA-9
20
Conclusions B: UV radiation &
Water/Water vapor permeabilities
 Polyurethane coatings present excellent resistance to
ultra violet radiation as compared to epoxy coatings that
suffer from yellowing. Both coatings present very low
water vapor transmission rate and liquid water
permeability.
 Radiation causes mild degradation to the acrylic and
elastomeric emulsions. Both coatings present fairly good
behavior towards moisture.
 The nanotechnology coating resists very well to radiation
and presents an improved behavior compared to all
other coatings systems regarding water vapor
transmission rate and liquid water permeability.
22/9/2014
eRA-9
21
Conclusions C: Carbonation
 The two-component industrial coatings with organic
solvent (epoxy and polyurethane coatings) provide the
best protection.
 Aqueous dispersions conventional coatings (elastomeric
and acrylic dispersions) offer a satisfying level of
protection.
 The nanotechnology coating provides a low and
negligible protection rate.
22/9/2014
eRA-9
22
Acknowledgements
This research has been co-financed by the European Union
(European Social Fund – ESF) and Greek national funds
through the Operational Program "Education and Lifelong
Learning" of the National Strategic Reference Framework
(NSRF) - Research Funding Program: ARCHIMEDES III.
Investing in knowledge society through the European Social
Fund.
22/9/2014
eRA-9
23
Thank you for your attention!
22/9/2014
eRA-9
24