Intergranular corrosion of aluminum

H. Kaesche, Pitting Corrosion of Aluminum and Intergranular Corrosion of Aluminum Alloys, Localized Corrosion NACE 3, R.W. Staehle, B.F. Brown, J. Kruger, and A. Agrawal, Ed., National Association Corrosion Engineers, 1974, p 516-525... 

H. Kaesche, Pitting Corrosion of Aluminum and Intergranular Corrosion of Aluminum Alloys, Localized Corrosion NACE 3, B.F. 

T. Ramgopal, P.I. Gouma, G.S. Frankel, Role of grain-boundary precipitates and solute-depleted zone on the intergranular corrosion of aluminum alloy 7150, Corrosion 58 (2002) 687—697. 

ASTM Standard G 67, Standard Test Method for Determining the Susceptibility to Intergranular Corrosion of 5XXX Series Aluminum Alloys by Mass Loss After Exposure to Nitric Acid, Annual Book of ASTM, 1999, 03.02. 

Fifty years ago, intergranular corrosion of the zinc—4% aluminum casting alloys was a problem because of high impurity levels, notably of lead, tin, and cadmium. The subsequent introduction of 99.99% zinc as the base for these casting alloys eliminated intergranular corrosion under normal service conditions. However, an inherent tendency for intergranular corrosion exists, and this defect can still occur if pure zinc-aluminum alloys are exposed to temperatures above about 70°C under wet or damp conditions. Research has... 

Fig. 1.13 Effect of intergranular corrosion of zinc-aluminum alloys on impact strength (Noranda, 1986).

Raising the temperature increases die dissolution of zinc and the ZA alloys (Belisle and DuFresne, 1986) in water. A marked increase occurs up to about 60°C, followed by a decrease at higher temperatures. Intergranular corrosion of the zinc-aluminum casting alloys is a risk above about 70 C in wet or humid conditions (e.g., in steam), when no protective layer can form and selective dissolution of the structure occurs. A steam test at 95°C is indeed a standard method of checking whether alloys have been correctly produced. 

Devillers, J. P., andNiessen, P. (1976a). The mechanism of intergranular corrosion of dilute zinc-aluminum alloys in hot water. Corros. Set., 76(4), 243-252. 

The effect of grain-boundary imperfections on intergranular attack is illustrated by the attack of hydrochloric acid on high-purity (99.998 %) aluminum (Fig. 1). Corrosion varies with the curvature of the boundary. Corrosion may be intensified by equilibrium segregation of traces of iron and/or copper impurity in zones at the boundary with high concentrations of imperfections. For example, corrosion of aluminum in hydrochloric acid is increased by a factor of 1000 in the presence of 0.03 % iron [3]. 

A rather unique mass loss test method, ASTM G 67 (Test Method for Determining the Susceptibility of Intergranular Corrosion of 5xxx Series Aluminum Alloys by Mass Loss After Exposure to Nitric Acid [NAMLT Test]) has been developed to provide a quantitative measure of the intergranular susceptibility of 5xxx series Al-Mg and Al-Mg-Mn allo3rs. The technique is useful to determine whether material has become sensitized by exposure to elevated temperature. Development of the test is reported in Ref 23. 

B.W. Lifka and D.O. Sprowls. 1972. Significance of intergranular corrosion of high strength aluminum alloy products. ASTM Special Publication 516, Localized Corrosion, Cause of Metal Failure, pp. 120-144. 

Effect of intergranular corrosion of zmc-aluminum alloys on impact strength. 

The research on corrosion, started in this institute in the 1950s, continued successfully further. The intergranular corrosion of steels was measured by an electrochemical potentiodynamic reactivation method [310-312]. Since the 1960s, the passivity of brass was further studied, the rates of corrosion were measured by polarization resistance, the effect of deformation on anodic dissolution of steels was followed, and the surface roughness of metals was measured other subjects of research were, e.g., the behavior of passive films on steel, the effect of compositirai and motion of electrolyte on corrosion of passivated aluminum, the cathodic protection of passive metals against corrosion, the anodes for cathodic protection of steels, etc.[313-316]. Measurements of polarization resistance in the system iron—concentrated sulfuric acid or boiling nitric acid, of corrosion and matter... 

All metals and alloys are joined together by grain boundaries. The intergranular corrosion of steels, brasses, bronzes and aluminum alloys containing copper is of particular interest to engineers. Because of the importance of steels, the largest amount of work reported in the literature is on steels. It would be, therefore, appropriate also here to review the phenomenon of intergranular corrosion with a particular emphasis on steels. It would be appropriate, hence, to review... 

ASTM G66 - test method for visual assessment of exfoliation corrosion susceptibility of 5xxx series aluminum alloys (Asset Test). ASTM G67 - test method for determining the susceptibility to intergranular corrosion of 5xxx series aluminum alloys by mass loss after exposure to nitric acid (Namlt Test). 

Intergranular and Exfoliation Corrosion, Corrosion of Aluminum and Aluminum Alloys, J.R. Davis, Ed., ASM International, 1999, p 63-74... 

Tests for aluminum and its alloys consist of intergranular corrosion, stress corrosion cracking and corrosion fatigue as detailed below ... 

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