Nickel alloys in seawater

Syrett BC. Erosion corrosion of copper-nickel alloys in seawater and other aqueous environments - A literature review. Corrosion, 32(6), June 1976. 

Figure 6.13. Behavior of copper-nickel alloys in seawater [F. LaQue, J. Am. Soc. Nav. Eng. 53, 29 (1941)].

Figure 4. 1. Complex plane impedance diagrams for 90 10 Cu Ni alloy in flowing seawater as a function of exposure time. Flow velocity = 1.62m/sec, [O2] = 0.045 mg/1, specimen area = ll.OScm T = 26°C exposure time = 50h. (From B. C. Syrett and D. D. Macdonald, The Validity of Electrochmical Methods for Measuring Corrosion Rates of Copper-Nickel Alloys in Seawater. Reprinted with permission from Corrosion, 35, 11, [1979], NACE, Houston, TX.) Numbers next to each point to frequency in hertz.

B. C. Syiett and D. D. Macdonald [1979] The Validity of Electrochemical Methods for Measuring Corrosion Rates of Copper-Nickel Alloys in Seawater, Corrosion 35, 505-508. 

Figure 9 Resistance to pitting corrosion of high-alloyed steels and nickel alloys in seawater based on the pitting resistance equivalent (PRE) [5, 23]...

The corrosion resistance of nickel alloys has been extensively explored in seawater and saltwater (brackish water). Although stainless steel 316 is known to resist pitting in seawater, stainless steels are, in general, susceptible to pitting in the tidal zones of seawater. The nickel alloys, more expensive than steels, have been extensively used in seawater service. Inconel alloy 625 offers an excellent resistance to corrosion in seawater. It also offers an excellent resistance to SCC. Nickel alloys are best used for pump shafts, bodies and impellers while other materials, like 90-10 Cu-Ni and austenitic steels are used for other parts, such as heat exchangers and valves. Table 9.47 shows the classification of selected nickel alloys in seawater service. 

Corrosion behavior. General corrosion rates for 90-10 and 70-30 copper-nickel alloys in seawater are low, ranging between 25 and 2.5 p,m y 1. For the majority of applications, these rates would allow the alloys to last the required hfetime, and there would be little probability of their premature failure in service due to such a corrosion mechanism. ... 

Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments, G 78, Annual Book of ASTMStandards, ASTM, 1992, p 463-470... 

It is pertinent that the 30% Ni-Cu alloy is relatively resistant to stress-corrosion cracking compared to the 10 or 20% Ni-Cu alloys [42], or compared to any of the 30% Zn-Cu brasses. A detailed general account of the behavior of copper-nickel alloys, especially the 10% Ni-Cu alloy, in seawater is given by... 

Removal of the corrosion product or oxide layer by excessive flow velocities leads to increased corrosion rates of the metallic material. Corrosion rates 2ire often dependent on fluid flow and the availability of appropriate species required to drive electrochemical reactions. Surface shear stress is a measure of the force applied by fluid flow to the corrosion product film. For seawater, this takes into account changes in seawater density and kinematic viscosity with temperature and salinity [33]. Accelerated corrosion of copper-based alloys under velocity conditions occurs when the shear surface stress exceeds the binding force of the corrosion product film. Alloying elements such as chromium improve the adherence of the corrosion product film on copper alloys in seawater based on measurements of the surface shear stress. The critical shear stress for C72200 (297 N/m, 6.2 Ibf/ft ) far exceeds the critical shear stresses of both C70600 (43 N/m, 0.9 Ibf/ft ) and C71500 (48 N/m, 1.0 Ibf/ft ) copper-nickel alloys [33]. 

S] Syrett, B. C., The Mechanism of Accelerated Corrosion of Copper-Nickel Alloys in Sulfide-Polluted Seawater, Corrosion Science. Vol. 21, 1981, p. 187. 

Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride Containing Aqueous Environments... 

The application of this technique for evaluating the longterm corrosion behavior of copper-nickel alloys in sulfide-polluted and unpolluted seawaters employed an intentional abrupt change of current between anodic and cathodic values to determine the feasibility of using the CRC method. 

Reda, M. R., and Alhajji, J. N., Comparison of Current Reversal Chronopotentiometiy (CRC) and Small Amplitude Cyclic Voltammetry (SACV) Method to Determine the Long-Term Corrosion Tendency of Copper-Nickel Alloys in Polluted and Unpolluted Seawater Under Jet-Impingement Conditions, Corrosion Testing in Natural Waters Second Volume, ASTM STP 1300,1997, pp. 143-158. 

ASTM G 78, Guide for Crevice Corrosion Testing of Iron Base and Nickel Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environment, descrihes the use of multiple crevice assemblies and other devices applicable to nickel alloy testing in chloride environments. These procedures can be used to identify conditions most likely to result in crevice corrosion and provide a basis for assessing the relative resistance of various alloys to crevice corrosion under certain specified conditions. 

Table 33 Corrosion rates for austenitic nickel cast alloys in seawater and salt solutions [91,93]...

In tropical waters, the corrosion values for nickel are higher than in the temperate climatic zones. The pitting depths reach approx. 3 mm after only 1 year, after which the penetration rate drops. Figure 43 and Figure 44 show the results of exposure tests of nickel and nickel alloys in the seawater of the Panama Canal Zone. Whereas in the immersion zone pitting depths of over 3 mm were reached, the values in the tidal zone were about 1.6 mm [192]. 

Table 63 provides an overview of the behaviour of nickel-based alloys in seawater, listed under their commercial names examples of their applications are listed in [204]. 

Crevice corrosion behaviour of high-alloyed austenitic steels and nickel-base alloys in seawater with and without addititon of chlorine EUROCORR, European Corrosion meeting, Volume 2 (1994), p. 143-154 Chameleon Press, London 1185] Eranz, E. Heitz, E. Herbsleb, G Schwenk, W. 

The two main wrought copper-nickel alloys chosen for seawater service contain 10 and 30% percent nickel, respectively. When comparing international specifications, the compositional ranges of the two alloys vary slightly between specifications, as can be seen in Tables 8.15 and 8.16 for 90-10 and 70-30 copper-nickel alloys. In practice, these variations have little influence on the overall service performance of the alloys. Iron is essential for both alloys because it provides added resistance to corrosion caused by velocity effects called impingement attack. An optimum level is between 1.5 and 2.5% iron, probably as a result of solid solubility. The corrosion resistance improves with increasing iron so long as it remains in solid solution. The specification limits for alloys were set by this observation. 

Nickel—Copper. In the soHd state, nickel and copper form a continuous soHd solution. The nickel-rich, nickel—copper alloys are characterized by a good compromise of strength and ductihty and are resistant to corrosion and stress corrosion ia many environments, ia particular water and seawater, nonoxidizing acids, neutral and alkaline salts, and alkaUes. These alloys are weldable and are characterized by elevated and high temperature mechanical properties for certain appHcations. The copper content ia these alloys also easure improved thermal coaductivity for heat exchange. MONEL alloy 400 is a typical nickel-rich, nickel—copper alloy ia which the nickel content is ca 66 wt %. MONEL alloy K-500 is essentially alloy 400 with small additions of aluminum and titanium. Aging of alloy K-500 results in very fine y -precipitates and increased strength (see also Copper alloys). 

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