Corrosion alloying, effect

To ensure maximum continuity of the tin-iron compound layer between tin and steel. This layer is itself corrosion resistant and appears to act as a nearly inert screen limiting the area of steel exposed as tin is removed by corrosion. Its effectiveness is measured by the Alloy-Tin Couple (A.T.C.) test, in which the current flowing is measured between a sample of tinplate from which the unalloyed tin layer has been removed, and a relatively large tin electrode immersed in an anaerobic fruit juice. ... 

With galvanoaluminum coatings like zinc-nickel alloys, long duration times were reached. Regarding thermal and mechanical stress, the corrosion-protective effect of the zinc-nickel alloy layers is clearly inferior to that of galvanoaluminum. The short life span of IVD-aluminum deposits in comparison to galvanoaluminum is notable. This difference may result from the different microstructures of these two types of aluminum coatings [97, 156]. 

Alternative deposited coatings involve thermal spray, such as plasma spray or two-wire arc [60]. Substrate alloy effects are minimal and coating chemistry and morphology can be designed for specific applications. Corrosion protection and good adhesive bond strength can be provided and maintained [61-64],... 

R.C. Newman, A theory of secondary alloying effects on corrosion and stress-corrosion cracking,... 

AUoy galvanic corrosion has been measured in alcohol fuel [27]. The corrosive effects of the alcohol fuels on different galvanic couples Zamak 5, low-carbon steel AISI 1010, stainless steel ABNT 420, and Al-Si alloy-4000 series were studied. Zamak was used as a permanent anode for these tests. Samples were immersion tested for three weeks at 50 °C. The alcohol fuel-water content was varied in this study and the corrosion product effect was investigated. Results indicated that higher ethanol fuel-water content was more corrosive regardless of the galvanic couples. 

Fig. 2.45 Five-year corrosion tests on early zinc-aluminum alloys effect of aluminum content on corrosion performance of aluminum-zinc alloy coatings after exposure in various atmospheres 1 mil = 25.4 p,m 1 ft 0.305 m (Zoccola et al., 1978).

The Corrosion Rate Break tests are followed by tests for corrosion inhibitor effectiveness at a produced water content above the Corrosion Rate Break level. At this point the decision is made on whether or not carbon or low alloy steel can be used, based on the corrosion rate data and corrosion inhibitor effectiveness coupled with estimates of future produced water levels during the life of the field. 

Guy D. Davis is a staff scientist and group leader of the Surface Sciences Department at Martin Marietta Laboratories. His current research interests include surface-sensitive measurements and their analyses, corrosion of aluminum and its alloys, effects of acid deposition on painted steel, formation and durability of adhesive bonds, and industrial failure analysis. Dr. Davis was the 1986 Distinguished Young Scientist of the Maryland Academy of Sciences. 

Zinc plating layers transformed by a heat treatment at 903 K (630 °C) completely into iron-zinc alloy phase (galvannealing) showed much better behaviour in the exposure zones. The corrosion protective effect of the hot-dip galvanised layers in seawater is thus not determined only by layer thickness, but also by the layer structure [216]. 

A major issue, for the passivation and corrosion resistance of aluminum alloys, is the existence or not of second phase inter-metallic particles resulting from alloying with elements that have low solubility in aluminum (Rynders et al., 1994 Kowal et al., 1996). These particles are detrimental to the resistance of the passive film to breakdown (the first stage of a localized corrosion process). In contrast to stainless steels, this factor often overwhelms the beneficial alloying effects. However, it must be pointed out that alloying elements such as copper in solid solution are beneficial (Muller and Galvele, 1977). Other elements, such as chromium, molybdenum, titanium, tantalum, and niobium, seem to improve the corrosion resistance of aluminum, but their solubility is too low for them to be used in conventional alloy processes, and they require the use of rapid quenching processes or some sort of nonequilibrium surface deposition. 

The addition of a minor element can also improve the resistance of copper-nickel alloys to erosion-corrosion. The effect of iron content on the corrosion and impingement resistance of 90/ 10 copper-nickel is maximized with the addition of about 2 percent... 

Sediment or debris can cause underdeposit corrosion or turbulence that can damage or remove the protective film, particularly on the less resistant copper-based alloys. Effective screening or filtering can limit this problem. Copper alloys are, in general, better at resisting the attachment of organisms than stainless steels or nickel alloys. 

The aggressivity of the environment is intimately related to fatigue Ufe. Increased concentration of a corrodant generally decreases the corrosion fatigue resistance of metals and alloys. For instance, in seawater, chemical, physical and biological factors affect the resistance of materials to corrosion. The effect of environment is shown in Fig. 4.67. It is to be observed that the corrosion fatigue limit in salt water is lower (30ksi) than in fresh water (40 ksi). 

Alloying elements of Mn, Al, Si, P, minimize flow induced corrosion of steels (annealed) in 3.0% NaCl, whereas C promotes corrosion. The effect of alloying elements on flow induced corrosion are shown in Fig. 9.14 [26]. 

Rosero-Navarro N.C., Curioni M., Bingham R., Duran A., Aparicio M., et al. (2010), Electrochemical techniques for practical evaluation of corrosion inhibitor effectiveness. Performance of cerium nitrate as corrosion inhibitor for AA2024T3 alloy , Corros. Set, 52, 3356-66. 

Turning to another area, mention will be made of the use of tin cans for various preserved foods. The tin may not always be made of tin plate there are other metals and alloys currently in use. In a recent publication from the Applied Research Laboratory of the U. S. Steel Corporation, R. P. Fran-kenthal( ) has described some most interesting results regarding corrosion of these materials. It must be remembered that cold-working exerts a considerable influence on the susceptibility of a metal to corrosion such effects have been known for quite a time. A great number of results from investigations into the role of deformation and surface treatment have been published in late years. 

Zarras et al. [950] described the use of poly(2,5-bis(A -Me-A -alkylamino))phenylene-vinylenes) coatings for corrosion protection of Al alloys. They studied these coatings via simple potentiostatic and galvanostatic electrochemical methods and found a significant corrosion-inhibition effect. 

S.R Lynch, S.R Knight, N. Birbilis, and B.C. Muddle, Stress corrosion cracking of Al-Zn-Mg-Cu alloys Effects of composition and heat treatment, in Proceedings of the 2008 International Hydrogen Conference Effects of Hydrogen on Materials, Jackson Hole, WY, 2008. 

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