Abstract

PAREDES-DUGARTE, Solange; HIDALGO-PRADA, Benjamín; AVILA-GODOY, Rosario  and  BRICENO-VALERO, Mauro. Study of pitting corrosion of the commercial aluminium alloy AA3003 in saline environment. Rev. Téc. Ing. Univ. Zulia [online]. 2007, vol.30, n.Especial, pp.168-177. ISSN 0254-0770.

The behavior of the commercial aluminum alloy CVG-ALCASA AA3003 in saline environment was studied. Salt spray tests (ASTM B117) were carried out and the pitting corrosion results were evaluated by optical interferometry, scanning electron microscopy and x-ray microanalysis. The results show that the distribution of the second phase particles of intermetallics α-Al₁₅(Fe,Mn)₃Si and  β-Al₆(Fe,Mn) controlled the nucleation of pits and the selectivity of the preferential nucleation sites. The α-Al₁₅(Fe,Mn)₃Si had a cathodic behavior, producing a strong interaction with the anodic aluminum matrix by rising the local alkalinity of the area around the particle. The  β-Al₆(Fe,Mn) exhibited a cathodic/inert behavior. This particular corrosion behavior in Al-Mn alloys have been attributed to the variations of the Mn/Fe ratio in the second phase intermetallics. The fluctuations in the pit’s average depth as a function of the time of exposure to the saline fog also show the random distribution of the galvanic micro cells based on intermetallics/matrix interactions presents in the surface of the material on the depth of the pits. It is concluded that the cold rolled AA 3003 (Al-Mn) studied is highly susceptible to a localized alkaline corrosion process assisted by second phase intermetallics, when it is exposed to saline environment.

Keywords : Aluminum alloy AA3003; pitting corrosion; intermetallics; optical interferometry; scanning electron microscopy.