Intergranular corrosion of an aluminum-magnesium-silicon-copper alloy

Journal Article · Sun Jan 01 04:00:00 EST 1995 · Corrosion

DOI:https://doi.org/10.5006/1.3293577· OSTI ID:187051

Burleigh, T D ^[1]; Ludwiczak, E; Petri, R A ^[2]

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1. Univ. of Pittsburgh, PA (United States). Materials Science and Engineering Dept.
2. Alcoa Technical Center, Alcoa Center, PA (United States)

The intergranular (intercrystalline) corrosion (IGC) of a heat-treated aluminum-magnesium-silicon-copper alloy was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM revealed that tall chimneys of corrosion product formed on the surface above the pits during oxygenated salt water immersion. It was postulated that pitting corrosion occurred first and that the corrosion chimneys maintained the acidic, chloride pit environment that subsequently caused IGC (preferential dissolution of the region adjacent to the grain boundaries). TEM foils of the same alloy were immersed in a model pit solution (dilute hydrochloric acid) and showed IGC identical to the corrosion attack seen in the bulk samples. Potentiodynamic polarization in the dilute HCl solution verified that pure Al corroded many times faster than the bulk alloy. These results indicated IGC of this alloy occurred because the depleted region adjacent to the grain boundaries corroded rapidly in acidic solutions. The presence of pits with corrosion chimneys, or some type of occluded cells, must have maintained the acidic environment, which caused IGC.

• Sponsoring Organization: USDOE
• OSTI ID: 187051
• Journal Information: Corrosion, Journal Name: Corrosion Journal Issue: 1 Vol. 51; ISSN 0010-9312; ISSN CORRAK
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
42 ENGINEERING
ALUMINIUM BASE ALLOYS
COPPER ALLOYS
CORROSION PRODUCTS
CORROSIVE EFFECTS
HEAT TREATMENTS
INTERGRANULAR CORROSION
MAGNESIUM ALLOYS
MORPHOLOGY
SEAWATER
SILICON ALLOYS