Review—Corrosion-Resistant Metastable Al Alloys: An Overview of Corrosion Mechanisms

Abstract

Commercial aluminum alloys exhibit localized corrosion when exposed to environments containing aggressive anions. Alloying of Al with specific elements (M: Cr, Mo, V, Nb, etc) using non-equilibrium processing techniques has been reported to result in significantly improved corrosion resistance due to the formation of a supersaturated solid solution and uniform distribution of M in the matrix. Several theories describing the corrosion behavior of Al–M alloys have been postulated. This paper presents an overview of the most common non-equilibrium alloying techniques implemented for the production of the metastable Al–M alloys and posited corrosion mechanisms for the improved corrosion resistance.

Corrosion behavior of an in situ consolidated nanocrystalline Al-V alloy

“…The corrosion resistance of the ball-milled Al alloys was high despite a nonuniform microstructure. The improved corrosion resistance of these Al alloys was hypothesized due to one or more of the following mechanisms, which are proposed based on the literature on the sputter-deposited Al alloys, ball-milled alloys Al, and stainless steels 4,[12][13][14] .…”

Cerium sulfate preparation from Egyptian monazite's rare earth cake for its application as corrosion inhibitor of aluminum alloy AA6061

“…Different stripping agents such as: (cold water, hot water, 2.0M H2SO4 and 2.0M HNO3) were studied at A/O volume ratio of 1/1 and equilibrium time 5 min. The obtained data in figure (2) revealed that, H2SO4 solution is the most effective agent for Ce stripping with efficiency of 82.2%.…”

“…Different O/A volume ratios ranging from 1/3 to 3/1 were studied by contacting the nitrate solution with 15% TBP in kerosene at pH of 1.7 and 7min equilibrium time. The obtained data in table (2) emphasized that, although the extraction efficiencies of Ce(IV) increased to 92.1 and 94.9% at O/A ratios of 2/1 and 3/1, respectively; but these ratios were not applied because the loaded Ce(IV) was diluted in the organic phase. On the other hand, the O/A ratios of 1/2 and 1/3 showed lower extraction efficiencies of Ce(IV).…”

“…Also, AA6061 is commonly used for construction of aircraft structures such as wings and fuselages, yacht construction, automotive parts and aluminum cans for the packaging of foodstuffs and beverages. In aluminum alloys, the alloying elements introduce heterogeneity into the microstructure, which is the main cause of localized corrosion that initiates in the form of pitting [2][3][4]. The electrochemical behavior of AA6061 in 3.5% NaCl in the absence and presence of some rare earth elements (REEs) has been studied by means of polarization curves and impedance measurements.…”

Electrochemical Behavior of Al–Al9Co2 Alloys in Sulfuric Acid

“…It has been stated that the presence of oxidized species of TMs in the alumina-based surface layer improve the corrosion resistance of Al-TM alloys, aluminides, and Al-based CMAs in chloride solutions and sulfuric acid solutions by blocking the aggressive-ion entry sites in the passive layers [59][60][61] or stabilizing the passive layers [62]. Recently, Esquivel and Gupta [63] summarized the proposed mechanisms for the contribution of TMs in the passivation ability of Al-TM alloys prepared by non-equilibrium processing techniques. Here, it should be noted that the similarity in the i p1 values of the high-Co alloys (10-20 wt.% Co), may be justified by the following reasoning: The increase in i p1 (stage 2) due to the decrease in the passive surface area, i.e., Al matrix, can to some extent counterbalance the decrease in i p1 due to the increase in the dissolved (in the matrix) Co content.…”