Corrosion behaviour of copper alloys
in natural sea water and polluted sea water
H. Le Guyader, A.M. Grolleau, V. Debout
DCNS CHERBOURG-CETEC -Code 0981 BP 440
50 104 CHERBOURG OCTEVILLE France
J.L. Heuzé, J.P Pautasso
DGA/DET/CEP
7-9 rue des Mathurins
92 220 BAGNEUX
ABSTRACT
Copper based alloys are frequently used in marine water systems. They have indeed an
attractive price and offer interesting mechanical characteristics associated to a relatively
good resistance to corrosion in sea water. Nevertheless, they can suffer from certain forms
of corrosion such as localised corrosion with sulphides pollution, crevice corrosion, or stress
corrosion cracking in sea water more or less polluted with ammonia.
A high strength copper nickel alloy (Nibron) and a Nickel Aluminium Bronze (A45) are
respectively compared to classical CuNi 90-10 (CuNi10Fe1Mn) and CuAl9Ni3Fe2,
elsewhere well known for their experimental feedback in sea water.
Standard electrochemical tests such as polarization resistance, open circuit potential
measurements and polarization curves are implemented in natural sea water and polluted sea
water. Static and under fretting crevice corrosion tests as well as specific stress corrosion
cracking tests with ammonia pollution are also conducted.
The copper alloys compared have shown rather similar behaviour in sea water. In near
stagnant conditions, risk of corrosion initiation in sea water is high with these alloys
(localised corrosion, crevice corrosion close to the gasket, corrosion under deposit, stress
corrosion cracking).
Usual recommendations for the use of copper alloys in sea water (ie passivation in clean sea
water, suitable range of flow rate, biocide treatment) must be strictly followed in order to
limit localised corrosion.
KEYWORDS: corrosion tests, copper alloys, natural sea water, polluted sea water
1
INTRODUCTION
Copper based alloys are frequently used in sea water system for applications such as heat
exchangers, pumps, valves, pipes, fasteners. Depending on the applications and the need for
mechanical characteristics, CuNi alloys (ie CuNi10Fe1Mn) or Nickel Aluminium Bronzes
can be used. Despite the emergence in recent years of other materials that offer improved
properties such as stainless steels, based nickel alloys or titanium, copper alloys continue to
be widely used. They have indeed an attractive price and offer interesting mechanical
characteristics associated to a relatively good resistance to corrosion in sea water.
Nevertheless, they can suffer from certain forms of corrosion such as localised corrosion
with sulphides pollution [1-6], crevice corrosion in valves or flanges assemblies [7-9]. Some
cases of stress corrosion cracking in sea water more or less polluted with ammonia were also
reported [10-12].
This paper summarises the results of a comparative test campaign conducted in natural sea
water and polluted sea water on a high strength copper nickel alloy (Nibron compared to the
classical CuNi10Fe1Mn) and a Nickel Aluminium Bronzes (A45 compared to
CuAl9Ni3Fe2). Nibron and A45 being dedicated for fastener applications.
The following classical electrochemical tests were first conducted in natural sea water to
assess corrosion parameters in the absence of critical interface:
-Open circuit potential (Eoc) and polarization resistance (Rp)
-Anodic polarization curves
-Weight loss measurements and corrosion rates estimation.
Secondly, the influence of sulphide or ammonia pollutions was investigated through the
same approach.
Thirdly, critical interface that simulated flanges assemblies were considered and tested
through crevice corrosion potentiostatic tests with a potential imposed close to Eoc.
Then, as relative micro displacements could be generated in certain assemblies, comparative
tests regarding crevice corrosion initiation under fretting were also carried out.
Finally, as NAB could be susceptible to Stress Corrosion Cracking (SCC) in natural sea
water or polluted sea water with ammonia, SCC U-bend tests were conducted.
EXPERIMENTAL PROCEDURE
Materials
Nominal compositions and mechanical properties of the base materials used are found in
tables 1 and 2 with reference to certificate data, but also to analysis and mechanical tests
conducted by the CESMAN1 depending on the material considered.
Specimens conditioning
All specimens used were wet polished to a final finish with 600-grade SiC paper except
SCC specimens that were polished to a 240-grit finish, degreased in methanol, rinsed in
deionised water and then air dried. Prior to testing, all specimens were immersed in
circulating natural sea water (2l/min) during about one month. Sea water is pumped from
Cherbourg harbour with the temperature varying from 17°C to 20°C during the period of
tests.
1
CESMAN Centre d’Expertises des Structures et MAtériaux Navals (de DCNS)
2
Corrosion testing
Eoc and Rp measurements
Eoc and Rp measurements were conducted on specimens machined from bars with a flag
shape to enable electric connection out of them sea water, the dimensions being of 25 mm in
length and 25 mm in width. Eoc was measured with respect to Saturated Calomel reference
Electrode (SCE). Rp measurements were obtained with linear polarization data acquired
using a potentiostat by imposing a small amplitude potential of 15 mV around Eoc. The
sweep rate was 0.05 mV/s. Rp was taken as the slope of the I= f(E) curve near Eoc.
Triplicate specimens were weighted before immersion and after cleaning with descaling
solvents. Comparisons were made in each case with control specimens. Weight loss
measurements were used to estimate the corrosion rates in µm/year. Specimen examination
was conducted before and after cleaning. Tests were conducted in natural sea water during
about 3 months but also in polluted sea water with sulphides or ammonia. Sea water
pollution was simulated through Na2S addition of 10 ppm S2-, in quiescent sea water
(Contact time 30 min before recirculation) every day during 5 days. The results obtained in
non polluted circulating sea water were compared to those in polluted sea water after about
3 months of test. Ammonia additions were considered as another possible pollution that can
be encountered in stagnant conditions due to organic matter degradation. NH4OH was then
added to stagnant sea water up to 1700 ppm of NH3, renewed every 2 weeks during more
than one month. The results obtained in stagnant sea water renewed every 2 weeks were
compared to those in stagnant sea water polluted with ammonia.
Polarization curves
The anodic polarization curves were generated using a potentiostat, at a scan rate of 0.05
mV/s, from Eoc to 0.3 V vs. SCE. The tests were conducted on “flag specimen” of 25 mm
in length and 25 mm in width. Conditions of tests were the same as those selected for Eoc
measurements.
Static crevice corrosion tests
The crevice device, shown in fig 1, was used in order to simulate metal /gasket interfaces
such as flanges assembly under static conditions. The gaskets were aramid fiber gaskets and
the assemblies were tightened to a controlled torque of 25 N.m leading to a pressure about
20 N/mm2. It was lower than in service pressure but considered as a significant condition.
One of the metallic surface was enlarged to enable crevice initiation out of the interface as it
was generally observed in service. Potentiostatic tests, at ambient temperature, were
conducted during 73 days in circulating natural sea water under an imposed potential chosen
close to the Eoc measured.
Crevice corrosion tests under fretting
Assemblies used for crevice corrosion testing assisted by fretting consisted of three
specimens with cylindrical bosses fastened through their central hole with a controlled
pressure of 2 N/mm2 as shown in figure 2. The tests were performed in natural sea water at a
controlled temperature of 25°C. Micro–displacements of 10 microns were generated at a
frequency of 10 Hz for 2 or 3 hours. Potentiostatic tests were conducted increasing the
potential step by step. The first phase consist of waiting for steady current close to Eoc
potential, then implementing a fretting sequence and recording the corresponding current.
Then, potential was increased and the fretting sequence implemented. This step was
repeated until the current reached 10-4 to 10-3 Amps.
3
Stress corrosion cracking tests
U-Bend tests were conducted according to ISO 7539-3 standard (ref 13).Tests parameters
were selected with regard to those defined previously to estimate CuAl9Ni3Fe2 SCC
susceptibility in natural sea water and polluted stagnant sea water with aqueous ammonia
[14]. Specimens were bent to a bending radius of 14 mm. Test environments chosen were
natural sea water and stagnant sea water added with two concentrations of aqueous
ammonia: 170 ppm (0.01 mol/l) and 1700 ppm(0.1 mol/l). Cracks were indeed observed on
CuAl9Ni3Fe2 in these conditions after respectively 1000 h and 120 h of test duration(ref
14). Each specimen was duplicated and two test durations were selected, 1000 hours and
5000 hours (four specimens tested in each condition).
RESULTS AND DISCUSSION
Corrosion parameters in natural sea water (absence of critical interface)
Eoc measurements of Nibron compared to CuNi10Fe1Mn are given in Figure 3. In natural
sea water, Nibron Eoc is maintained around -250 mV vs. SCE over a period of time of about
one month. Then, Eoc increases to -70 mV vs. SCE after 2 months of test. The triplicate
specimens in test give the same results.
Rp measurements of Nibron , shown in Figure 4, confirms this tendency to corrosion
initiation with an initial value of 5000 to 10 000 Ohm decreasing to between 10 and 300
Ohm after 2 months of exposure to sea water. Nibron specimens examinations, presented in
Figure 5, shows green oxidation products significant of corrosion initiation. The mean
corrosion rate is nevertheless low around 18 µm/year. Pitting corrosion is observed but the
pit depths are too low to be estimated. After one month of exposure to natural sea water,
anodic polarization curves, in Figure 6, exhibit no actual passivation threshold, the current
density increases from 10-7 A/cm2 to about 10-5 A/cm2 up to a potential of -50 mV vs. SCE.
Over this potential, anodic current sharply increases to 10-3 A/cm2. If Nibron is compared to
the classical CuNi10Fe1Mn, mean corrosion rate could be considered similar respectively
18 µm/year and 15 µm/year but Nibron could have a higher tendency to pitting in natural
sea water. Eoc and Rp measurements confirm this different behaviour. CuNi10Fe1Mn
presents indeed a steady potential and Rp with time, respectively -200 mV vs. SCE and
2000 Ohm as Nibron shows an increase in potential over -100 mV vs. SCE and a decrease in
Rp under 100 Ohm after 2 months of exposure to sea water.
In conclusion, Nibron could be considered a bit more susceptible to corrosion and especially
localised corrosion than CuNi10Fe1Mn in natural sea water.
Eoc measurements of A45 compared to the NAB CuAl9Ni3Fe2 are given in Figure 7.
Similar phenomenon is observed on both alloys, that is an increase in potential from -250
mV vs. SCE to -90 mV vs. SCE after 2 months of exposure to sea water. At the same time,
Rp shown in Figure 8, presents similar evolution with a decrease from a steady value of
3000 Ohm to 100 Ohm after 2 months of test. Specimen examinations reveal a mean
corrosion rate of 37 µm/year with a localised corrosion observed near the coated electric
connection evaluated at 1.3 mm/year, the max. depth being of about 150 to 300 µm. Similar
observations are made on CuAl9Ni3Fe2. Anodic polarization curves performed on A45 and
CuAl9Ni3Fe2 , in Figures 9 and 10, are very similar. No actual passivation thresholds are
observed in both cases. For A45, current densities increase slowly from 10-6 A/cm2 to 10-5
4
A/cm2 between -220 mV vs. SCE and -100 mV vs. SCE. Then, over – 100 mV vs. SCE ,
current densities sharply increase to 10-3 A/cm2.
In conclusion, electrochemical behaviour of A45 and CuAl9Ni3Fe2 are very similar with a
higher tendency to localised corrosion of these both alloys compared to Nibron or
CuNi10Fe1Mn.
Influence of sulphides pollution on corrosion parameters
With suphides pollution, Eoc measured on Nibron shown in Figure 3 increases from - 250
mV vs. SCE to -70 mV vs SCE after 2 months of test, as it was observed in natural sea
water. At the same time Rp , in Figure 4, decreases to 100 Ohm. Specimen examination
after the test, reveals an important green oxides deposit as shown in Figure 5 with a mean
corrosion rate estimated about 49 µm/year. Nibron anodic polarization curve with sulphides
pollution is very similar to those of CuNi10Fe1Mn. Anodic current, in Figure 6, sharply
increases to 10-4 A/cm2 for a potential between -100 mV vs. SCE and -30 mVvs.SCE.
In conclusion, with sulphides pollution, Nibron presents a comparative behaviour to
CuNi10Fe1Mn. Compared to results in natural sea water, mean corrosion rates are increased
and affected areas are spread all over the exposed surface in both cases.
Influence of ammonia pollution on corrosion parameters
With ammonia pollution, A45 Eoc, shown in Figure 11, decreases from – 250 mV vs ECS to
-350 mV vs. ECS. This decrease in potential was checked on Pt Electrode. The same
phenomenon is also observed on CuAl9Ni3Fe2 (see Figure 12). Specimen examinations
after the tests reveal a superficial corrosion with no significant pitting. The mean corrosion
rates for A45 and CuAl9Ni3Fe2 are respectively 13 µm/year and 16 mm/year. Anodic
polarization curves performed on A45 and CuAl9Ni3Fe2, in Figure 9 and 10 reveal a
significant increase in current between -150 mV vs. SCE and – 250 mV vs. SCE in sea water
with ammonia pollution. The current densities reach 7.10-5 A/cm2.
In conclusion, these tests reveal the potential risk of galvanic coupling between a surface
polluted with ammonia and a large surface in unpolluted natural sea water.
Parameters of crevice corrosion initiation (Static tests) in natural sea water
Tests conducted on Nibron, under – 70 mV vs ECS in Figure 13, lead to a high current
around 10-3 A/cm2 after 100 hours of test. A uniform corrosion is observed, localised out of
the crevice interface. CuNi10Fe1Mn presents exactly the same phenomenon with lower
current about 5. 10-5 A/cm2 under a potential of -75 mV vs.ECS.
On A45, the current measured under – 100 mV vs SCE is 10-5 A/cm2 after 100 hours of test.
Then, it increases gradually to 10-4 A/cm2 (see Figure 14). Corrosion is observed out of the
crevice interface but localised at the edge of the gasket. A45 and CuAl9Ni3Fe2 show a very
similar behaviour.
In conclusion, the various materials tested show a certain susceptibility to crevice corrosion.
In each case, this corrosion is localised out of the crevice interface and close to the gasket
edge in the case of NAB.
5
Parameters of crevice corrosion initiation and propagation under fretting in natural sea water
On the Nibron crevice device, tests begin under a potential of -150 mVvs.SCE. As shown in
Figure 15, currents are maintained low (10-6 A) for a potential varying from – 150 mV vs
SCE to -100 mV vs SCE. Above these potential, currents become significant from -70 mV
vs SCE and reach 8. 10-4A. Fretting induces no significant increase in current. For imposed
potentials from -60 mV vs. SCE to -50 mV vs. SCE, corrosion currents are very high
(2.10-3A). After the tests, specimen examination, presented in Figure 16, reveals superficial
corroded areas at the periphery and corrosion initiates near the hole but this corrosion has
occurred during the initial immersion phase but not during the fretting step.
A comparative test conducted on CuNi10Fe1Mn with the results shown on Figure 17 and
18 leads to the same conclusions with no significant effect of the fretting observed. Initiation
potential is estimated around -70 mV vs. SCE under static conditions as under fretting.
Corrosion areas are also mainly located at the periphery of the specimen.
On A45 (see Figure 19), corrosion initiates naturally under free potential ( -105 mV vs.
SCE) at the beginning of the test. Under – 100 mV vs. SCE, the current reaches 2. 10-4 A
which is higher than those observed on Nibron and CuNi10Fe1Mn in the same conditions.
Under -80 mV vs. SCE, fretting has got an effect on the current measured: after a fretting
step of about one hour, corrosion current increases from 4.410-4 A to 6.2 10-4 A. From – 70
mVvs SCE, the current measured become very high (10-3 A) but similar under static
conditions and under fretting. Specimen examination, shown on Figure 20, reveals after the
fretting test a selective corrosion at the periphery of the specimen with dealuminisation, the
maximum corrosion depth being of 0.1 mm.
The comparative test conducted on CuAl9Ni3Fe2,in Figures 21 and 22, leads to similar
observations with lower currents measured. Under -100 mV vs. SCE, the current measured
is indeed 9 fold higher on A45. In both cases, A45 and CuAl9Ni3Fe2, fretting begins to be
effective from -80 mV vs SCE with high steady currents that reached respectively 6.2 10-4
A and 2.8 10-3A. The crevice corrosion test under static conditions previously presented,
seems to be less severe with corrosion current measured around 10-4 A under a potential of –
100 mV vs.SCE.
In conclusion, initiation potentials in static conditions and under fretting are similar but
fretting could have an effect on corrosion rates especially on A45 and CuAl9Ni3Fe2.
Globally corrosion initiated naturally during the immersion phase and propagated under
imposed potential essentially out of the crevice interface under fretting but also in static
conditions.
U-bend SCC tests in natural sea water and polluted sea water with ammonia
On A45, cracks initiate in sea water polluted with 1700 ppm of ammonia after 1000 hours of
tests as shown in Figures 23 and 24, but not in natural sea water and polluted sea water with
170 ppm of ammonia. By comparison, CuAl9Ni3Fe2, suffers from SCC in natural sea water
and polluted sea water with only 170 ppm of ammonia. Experimental feedback presented
previously [14] had confirmed the susceptibility CuAl9Ni3Fe2 in stagnant sea water in long
term service conditions. The test in sea water polluted with ammonia was considered as one
possible simulation of SCC phenomenon in stagnant sea water. In that conditions, A45
could be considered as susceptible to SCC in stagnant sea water but high concentrations of
ammonia are needed to reveal its susceptibility compared to CuAl9Ni3Fe2 so that it appears
less critical.
6
U-bend tests conducted on Nibron compared to CuNi10Fe1Mn, shown in Figures 25 and 26
has revealed no susceptibility of both alloys to SCC in natural sea water but also in stagnant
sea water possibly polluted with ammonia after 5000 hours of tests.
CONCLUSION
A comparative test campaign was conducted in natural sea water and polluted sea water on a
high strength copper nickel alloy (Nibron compared to the classical CuNi10Fe1Mn) and a
Nickel Aluminium Bronzes (A45 compared to CuAl9Ni3Fe2). The following conclusions
can be drawn from this study:
1. In natural sea water Nibron appears slightly more susceptible to corrosion than
CuNi10Fe1Mn, A45 and CuAl9Ni3Fe2 have a similar behaviour considering
electrochemical tests.
2. Sulphides pollution leads to a significant increase in corrosion on Nibron and
CuNi10Fe1Mn.
3. NH3 pollution increases the risk of SCC on A45 and CuAl9Ni3Fe2 as Nibron and
CuNi10Fe1Mn show no susceptibility to this form of corrosion.
4. Presence of gasket increases the risk of crevice corrosion initiation near the gasket but not
under the gasket, phenomenon more over observed in operating conditions.
5. Crevice corrosion initiation potentials are similar under static conditions and under
fretting. For A45 and CuAl9Ni3Fe2, fretting could have an effect on corrosion rates,
currents level are higher. Globally, corrosion can initiate naturally during the immersion
phase in sea water and propagate under imposed potential essentially outside interface
specially under fretting conditions but also in static conditions.
Globally, the copper alloys compared have shown rather similar behaviour. In sea water
near stagnant conditions, risk of corrosion initiation is high with these alloys (localised
corrosion, crevice corrosion close to the gasket, corrosion under deposit, stress corrosion
cracking). Usual recommendations for the use of copper alloys in sea water (ie passivation
in clean sea water, suitable range of flow rate, biocide treatment) must be strictly followed
in order to limit localised corrosion.
ACKNOWLEDGMENTS
The authors will gratefully acknowledge J Mawella (from MoD) and J Galsworthy (from
Qinetiq) for supporting the French/UK scientist exchange (British French Cooperation
Program) which significantly enhanced this study. This work was funded by the French
Ministry of Defence (DGA/DSA/SPN). B. Avaulée and E. Postaire are recognised for their
efforts in conducting the tests. The authors also express their appreciation to the whole
DCNS /CETEC/MCP staff for their participation to this work and like to thank JM Corrieu
from CESMAN for assistance in material chemical analysis and mechanical evaluations.
REFERENCES
1. BC SYRETT, Sulfide attack in steam surface condensers, Conf on environmental
degradation of engineering materials in an aggressive environment, Virginia Polytechnic
Institute, 1981
7
2. AM BECCARIA, G POGGI, P TRAVERSO , A study of 70Cu30Ni commercial alloy
in sulphide polluted and un polluted sea water, Corrosion Science vol 32, N°11, 1991,
P1263
3. JN Al-HAJJI and MR REDA , The corrosion of copper nickel alloys in sulfide polluted
sea water: the effect of sulfide concentration, Corrosion science Vol 34 n°1, 1993,p163
4. DR LENARD and RR WELLAND, Corrosion problems with copper nickel components
in sea water systems , paper 599 , Corrosion 98
5. DR LENARD, The effect of decaying organisms on the corrosion of copper nickel
alloys in sea water, paper 02185, Corrosion 2002
6. A KLASSERT, L TIKANA Copper and copper nickel alloys- an overview Eurocorr
2004
7. RM KAIN, BE WEBER, Effect of alternating sea water flow and stagnant layup
conditions on the general and localized corrosion resistance of CuNi and NiCu alloys in
marine service, paper 422, Corrosion 97,
8. AYLOR OM, HAYS RA, KAIN RM, Crevice performance of candidate naval ship sea
water valve materials, paper 329 , Corrosion 99,
9. H HOFFMEISTER, J ULLRICH, Quantitative effect of transient potentials and
temperature on crevice corrosion of Naval Cast CuNiAl Valve bronze in natural sea
water Corrosion 2000
10. JOSEPH G , PERET R, OSSIO M , Copper and Al Cu Stress Corrosion in artificial sea
water,10th international congress on metallic corrosion Vol V Madras India 8912-720599 pp185-197 DP 1989
11. G JOSEPH, Stress corrosion cracking susceptibility of alpha aluminium bronzes in
sodium chloride solutions. 1-3 oct 1990 VASTERA CONGR CENTER 9103-72-0162
pp447-493 DP 1990
12. KUNIGAHALLI L VASANTH AND RICHARD A HAYS. Corrosion assessment of
Nickel Aluminum Bronze (NAB) in sea water. Corrosion 2004 paper 04294.
13. ISO 7539-3-Corrosion of metals alloys-Stress corrosion testing-part 3: Preparation and
use of U-bend specimens
14. H LE GUYADER, A.M GROLLEAU, JL HEUZE, V DEBOUT. Stress Corrosion
Cracking susceptibility of Nickel Aluminium Bronzes in Natural Sea Water , Eurocorr
2005 , Paper 38 Lisbon
8
Material
Nibron
According to
CESMAN
analysis
CuNi10Fe1Mn
Certificate data
A45
Certificate data
Al Zn Ni Fe Mn Impur Si
Sn+Pb P
C
S
Cu
2.53 0.006 13.8 1.06 0.43
0.004 0.0010 <0.0 0.004 <0.001 82
(Pb)
03
9.96 0.01 4.80 3.28 0.55 0.04
Nil
0.15
(Sn)
CuAl9Ni3Fe2
Certificate data
8.8 0.01 2.7
0.03
0.02
(Sn)
0.001
(Pb)
0.006 10.5 1.7
0.87 0.04
2.1 1.37 0.04
0.004 0.015 0.009 0.005 Bal
Bal
(incl
Ag)
Bal
Table 1: Chemical composition of the base metal alloys (% in weight)
Material
0.2% YS
(MPa)
UTS
(MPa)
Elongation
%
Hardness
Average value
CuNi10Fe1Mn
Certificate data
129
320
42.6
90 (HB)
Nibron according
to CESMAN tests
CuAl9Ni3Fe2
Certificate data
A45
According to
CESMAN tests
579
811
17.5
251
576
54
640
810
20
Table 2: Mechanical properties of the base metal alloys
9
137(HB)
Titanium bolt and screw
Aramid fiber
gasket
diameter 30 mm washer
Titanium plate
•polished to a 600-grit finish
•Controlled pressure 20 N/mm2
Figure 1 : Static crevice test device
Corrosion current monitoring
Displacement
Generator
Potentiostat
Potential
monitoring
Figure 2 : Crevice Corrosion test bench under fretting
10
0
CuNi Na2S pollution
after 1 month in natural sea
-50
Nibron in natural sea water
E in mV/ECS
-100
Nibron Na2S pollution
after 1 month in natural sea water
-150
CuNi in natural sea water
-200
-250
-300
-2
5
12
19
26
33
40
47
54
61
68
75
82
89
96
103
110
Time in days
moyenne nibron eau de mer
moyenne CuNi90-10 eau de mer
moyenne Nibron eau de mer polluée après 1 mois
moyenne CuNi 90-10 en eau de mer polluée après 1 mois
Figure 3 : Eoc in natural sea water and polluted sea water with sulphides
Comparison between Nibron and CuNi10Fe1Mn
10000
CuNi in natural sea water
Rp in Ohms
1000
CuNi Na2S pollution(10 ppm)
after 1 month in natural sea water
100
Nibron in natural sea water
10
Nibron Na2S pollution(10 ppm)
after 1 month in natural sea water
1
0
7
1
2
2
3
4
4
5
6
7
7
8
9
9
10
Time in
Time
in days
days
moyenne Nibron en eau de mer
moyenne CuNi 90-10 en eau de mer
moyenne Nibron en eau de mer poluuée après 1 mois
moyenne CuNi90-10 en eau de mer poluuée après 1 mois
Figure4 : Rp in natural sea water and polluted sea water with sulphides
Comparison between Nibron and CuNi10Fe1Mn
11
11
Nibron test in natural sea water sea water
Nibron Na2S pollution
Mean corrosion rate = 49µm/year.
Mean corrosion rate = 18µm/year.
CuNi90-10 Na2S pollution.
CuNi90-10 test in natural sea water
.
Mean corrosion rate = 15µm/year.
Mean corrosion rate = 52µm/year.
Figure 5 : Specimen examination after exposure to natural sea water and polluted sea
water with sulphides
Comparison between Nibron and CuNi10Fe1Mn
1,00E-02
1,00E-03
Nibron after 1 month
in natural sea water
CuNi after 1 month
in natural sea water
current density en A/cm²
1,00E-04
1,00E-05
1,00E-06
CuNi after 1,5 month in natural
seawater + Na2S pollution 10 ppm
1,00E-07
1,00E-08
Nibron after 1 month in natural
seawater + Na2S pollution 10 ppm
1,00E-09
1,00E-10
-0,3
-0,2
-0,1
0,0
E/ECS in V
0,1
0,2
0,3
0,4
B5 après 1 mois en eau de mer propre
CuNi90/10 après 1 mois en eau de mer propre
Nibon après 1 mois en eau de mer propre puis pollution Na2S
CuNi 90-10 après 1 mois1/2 en eau de mer propre puis pollution Na2S
Figure 6: Anodic polarization curves after exposure to natural sea water and polluted sea
water with sulphides
Comparison between Nibron and CuNi10Fe1Mn
12
0
-50
CuAl
-100
A45 AMPCO
-200
-250
-300
CuAl9 Ni3 Fe2
-350
mean corrosion rate = 58 µm/year
mean localised corrosion rate=1.13 mm/year.
-400
0
7
14
21
28
35
42
49
56
63
70
77
84
91
Test duration in days
moyenne A45
moyenne CuAl
Figure 7: Eoc in natural sea water
Comparison between A45 and CuAl9Ni3Fe2
10000
A45
1000
Rp in Ohms
E/ECS in mV
A45
mean corrosion rate = 37 µm/year
mean localised corrosion rate =1.3 mm/year
-150
CuAl
100
10
0
7
14
21
28
35
42
49
56
63
70
77
84
Test duration in days
moyenne A45
moyenne CuAl
Figure 8: Rp in natural sea water-Comparison between A45 and CuAl9Ni3Fe2
13
A45 - natural seawater + NH3 pollution (1700 ppm)
at ambient temperature
1,00E-02
- A45 one month in circulating natural seawater
(reference)
current density (A/cm²)
1,00E-03
1,00E-04
459
455
1,00E-05
4523
1,00E-06
- A45 one month in circulating natural seawater then seawater
treated with NH3 (1700 ppm)
1,00E-07
-A45 one month and 3 weeks in circulating seawater
then tseawater teated with NH3 (1700ppm)
1,00E-08
-400
-300
-200
-100
0
100
200
300
400
E (mV/SCE)
Scanning rate 0.05 mV/s
Figure 9: A45 Anodic polarization curves after exposure to natural sea water and polluted
sea water with ammonia
CuAl9Ni3Fe2 - Natural seawater + NH3 pollution (1700 ppm) at 20°C
1,00E-02
Natural seawater
1,00E-03
current density (A/cm²)
1,00E-04
1,00E-05
C23
1,00E-06
C6
C25
1,00E-07
C23 in natural seawater one month before NH3 treatment ( 1700 ppm)
1,00E-08
C25 in natural seawater one month and a half before
NH3 treatment ( 1700 ppm )
1,00E-09
-400
-300
-200
-100
0
100
200
300
400
E (m V/SCE)
scanning rate 0.05 mV/s
Figure 10: CuAl9Ni3Fe2
Anodic polarization curves after exposure to natural sea water and polluted sea water
with ammonia
14
test duration (h)
(1 month +3 w eeks)
0
0
500
OC potential (mV vs SCE)
-50
1000
circulating natural seawater
1500
2000
2500
3000
E 459
NH3 treatment (T min=20°C - Tmax=25°C)
E 4522
E 458
-100
E 4557
E 4523
Corrosion initiation
-150
E 457
E 4558
t r aet ment n°1
-200
t r eat ment n°2
-250
-300
t r eat ment n°3 t r eat ment n°4
-350
-400
Figure 11: A45 Eoc in natural sea water and polluted sea water with ammonia
test duration (h)
1 month
0
0
500
1000
1500
corrosion initiation
after 60 days
-50
2000
2500
3000
C7 et C9 in natural seaw ater
corrosion
-100
corrosion initiation after 70 days
OC potential (mV/SCE)
-150
E C22
E C23
E C24
-200
E C7
E C9
-250
2nd treatm ent*
3rd treatm ent
4th treatm ent
-300
-350
1st treatm ent
-400
-450
5 th treatm ent
circulating SW
C22,C23,C24: Seaw ater w ith NH3 treatm ent - 1700 ppm (18°C-25°C)
-500
Figure 12: CuAl9Ni3Fe2
Eoc in natural sea water and polluted sea water with ammonia
15
1,0E+00
-40
- 50 mV/ECS
-60
1,0E-01
-80
-100
Nibron
1,0E-02
Nibron
-120
1,0E-03
-140
Potential/SCE in mV
current in Amps
- 70 mV/ECS
-160
1,0E-04
CuNi 90/10
-180
CuNi 90/10
1,0E-05
-200
0
100
200
300
400
500
600
700
800
900
Test duration(hours)
Figure 13
Crevice corrosion initiation in natural sea water (ambient temperature)
Comparison between Nibron and CuNi10Fe1Mn
CuAl9Ni3Fe2
1,00E-04
Current in Amps
-100
- 100 mV/ECS
-150
A45
1,00E-05
-200
1,00E-06
-250
1,00E-07
-300
1,00E-08
-350
CuAl9Ni3Fe2
A45
1,00E-09
0
100
200
300
400
-400
500
Test duration in hours
Figure 14
Crevice corrosion initiation in natural sea water (ambient temperature)
Comparison between A45 and CuAl9Ni3Fe2
16
Potential in mV/SCE
1,00E-03
1,00E-02
~47
h
1h
0
~71h
50
100
- Torque wrench : 2 N/mm²
- polish to a 600 grit finish
144 167,5h
h
150
411h
315h 339h
200
250
300
350
test duration (h)
0
400
450
500
-20
-50 m V
1,00E-03
- 60 m V
-40
-60
-70 m V
-80 m V
-80
I (A)
-90 m V
-100 m V
1,00E-04
-100
-120 m V
-120
10 µm - 10 hz- 1h
-140
-160
-180
E initial : -150 m V 10 µm - 10 hz- 1h
1,00E-06
E (mV/SCE)
1,00E-05
-200
Figure 15 : Nibron - Crevice corrosion test under fretting in natural sea water 25°C
After immersion in SW 3 Weeks
After tests on fretting test bench:
Slight corrosion at the circumference on
0.5 mm
(max depth. 30 µm)
Corrosion initiation
Taille image:
Taille image:
Corrosion initition:
(max depth 70 µm)
Lateral specimen
rep. 625-Ni-CF1-1
corrosion
No corrosion
Superficial corrosion at the
circumference
On 0.5 mm
(max depth . 20µm)
Central specimen
rep. 625-Ni-CF2-1 / face n°1
Figure 16 : Nibron – Specimen examination after crevice corrosion test under fretting in
natural sea water (25°C)
17
~70h
1,00E-02
0
50
~189h
98h
100
150
239h
200
250
Test duration(h)
0
300
350
- torque w rench: 2 N/mm²
- polishing to a 600 grit finish
1,00E-03
I i nitial = 5 10-5A
(under-100mV
before fretting)
-20
-50 m V
-50 m V
-60 m V
-60
-70 m V
-80 m V
-80
-100 m V
I (A)
-40
-100
-120
1,00E-04
-140
-180
1,00E-05
E (mV/SCE)
-160
10 µm - 10 Hz -1h
10 µm - 10 Hz -1h
-200
Figure 17 : CuNi10Fe1Mn - Crevice corrosion test under fretting in natural sea water
25°C
After immersion 3 weeks in natural SW
After tests on fretting test bench
Corrosion initiation
0.10
-Slight corosion on the surface
-Localised corrosion outside the interface close
-to the interface (max depth: 0.24 mm)
0.24
Lateral specimen
rep. 625-CN-CF1-1
0.10
Central specimen
rep. 625-CN-CF2-1/ face n°2
-
No corrosion
0.14
Superficial localised corrosion at the
circumference on 3 mm
(max depth : 0.03 mm)
And some pittings
(max depth 0 14 mm)
Figure 18 : CuNi10Fe1Mn – Specimen examination after crevice corrosion test under
fretting in natural sea water (25°C)
18
1,00E-02
~46h
0
166h
50
100
150
214h 238,5h
200
250
314h
300
337,5h
350
383h
400
Test duration (h)
0
450
-20
-50 mV
-60 mV
1,00E-03
-70 mV
-80
-90 mV
I (A)
-100 mV
-105 mV
-60
-100
-120
1,00E-04
-140
10 µm - 10 Hz-1h
-160
- Torque wrench: 2 N/mm²
1,00E-05
-180
- Polish to a 600 grit finish
-200
Figure 19 : A45 - Crevice corrosion test under fretting in natural sea water 25°C
After immersion 3 weeks in SW
After tests on fretting tes t bench
-corrosion out of the interface
Max depth 0.18 mm
pittings
(0.08 mm
0.16 mm*
0.16 mm*
.
-numerous slight pittings on the surface
of the interface (max depth : 0.08 mm)
0.18 mm*
Lateral specimen
rep. 625-A45-CF1-1
* Max
0.10 mm
-some corrosion at the circumference
On 1.6 mm
-rare pittings on the surface
(max depth : 0.10 mm)
Central specimen
rep. 625-A45-CF2-1 / face n°1
Figure 20 : A45 – Specimen examination after crevice corrosion test under fretting in
natural sea water (25°C)
19
E (mV/SCE)
-80 mV
-40
Test duration (h)
1,00E-02
20
0
-
0
40
60
Torque wrench : 2 N/mm²
80
100
120
140
160
180
200
220
240
-20
- Surface polishing to 600 grit finish
-40
1,00E-03
-60
-80 mV
inital = 4 10-6A
before fretting
I
10 µm - 10 Hz -4h
-80
10 µm - 10 Hz -1h
-100 mV
1,00E-04
-100
10 µm - 10 Hz -1h
-120
10 µm - 10 Hz -1h
10 µm - 10 Hz -1h
-150 mV
-140
1,00E-05
-160
-180 mV
-180
-200
1,00E-06
Figure 21 : CuAl9Ni3Fe2- Crevice corrosion test under fretting in natural sea water 25°C
After immersion in NSW 3 Weeks
After tests on fretting test bench
pitting
(0.11 mm)
Green oxides
Lateral specimen
rep.625-CA-CF1-4
Some superficial pittings
Localised corrosion
outsite the crevice
interface
(depth
maxi. 0.13 mm max)
No corrosion
some pittings at the cimcumference on 1.5 mm
(max depth 0.08 mm)
Central specimen
rep. 625-CA-CF2-2 / face n°1
Figure 22 : CuAl9Ni3Fe2 – Specimen examination after crevice corrosion test under
fretting in natural sea water (25°C)
20
Sea Water + 170 ppm NH3 - 1 000 hours
Cu Al9 Ni3 Fe2
Sea water + 1700 ppm NH3 - 120 hours
1 000 hours
44
Cracks
45
Cracks
5
No Cracks
6
Sea water + 170 ppm NH3
5 000 hours
A 45
7
No Cracks
8
No Cracks
9
1 000 hours
10
Sea water + 1700 ppm NH3
11
5 000 hours
No crack observed on A45 in natural sea water after 5000 h
as CuAl9Ni3Fe2 exhibits cracks after 7500 h
No Cracks
12
Cracks
Cracks
Cracks
Cracks
Figure 23 : A45 and CuAl9Ni3Fe2 -U-bend test results in natural sea water and polluted
sea water with ammonia
A45
Cu Al9 Ni3 Fe2
Specimen 45
Sea water + 1700ppm NH
3
Specimens 9 et 10
Sea water + 1700 ppm NH3 - 1000 hours
- 120 hours
125 µm
Cracks
50 µm
25 µm
Figure 24: A45 and CuAl9Ni3Fe2 -U-bend test results in natural sea water and polluted
sea water with ammonia- Specimen examinations
21
Sea water + 170 pp
C Ni 90 - 10
de
3
- 1 000
No cracks
17 et
Sea water + 1700 ppm de NH3 - 1 000
21 et
No cracks
Sea water + 170 ppm de NH3 - 5 000
19 et
No cracks
Sea water + 1700 ppm de NH3 - 5 000
23 et
No cracks
Sea water + 170 ppm de NH3 - 1 000
31 et
No cracks
Sea water + 1700 ppm de NH3 - 1 000
35 et
No cracks
Sea water + 170 ppm de NH3 - 5 000
33 et
Sea water + 1700 ppm de NH3 - 5 000
37 et
Nibron
No cracks
No cracks
No cracks on CuNi 90-10 and Nibron observed after 5000 hours in natural sea water
Figure 25: Nibron and CuNi10Fe1Mn -U-bend test results in natural sea water and
polluted sea water with ammoniaCuNi 90-10
Nibron
Specimen 20
seawater + 170ppm NH
3
Specimen 34
Seawater + 170ppm
- 5000 hours
250µm
NH 3 - 5000 Hours
250 µm
Specimen 37
Sea water + 1700ppm NH 3 - 5000 Hours
Secimen
24
Sea water + 1700ppm NH 3 - 5000 Hours
250 µm
250µm
Figure 26: Nibron and CuNi10Fe1Mn -U-bend test results in natural sea water and
polluted sea water with ammonia-Specimen examination
22