The influence of surface treatment on filiform corrosion resistance of painted aluminium alloy sheet

• Published in: Corrosion science Vol. 45; no. 8; pp. 1767 - 1777
• Main Authors: Zhou, X., Thompson, G.E., Scamans, G.M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2003; Elsevier Science
• Subjects: Aluminium; Applied sciences; Corrosion; Corrosion environments; Exact sciences and technology; Filiform corrosion; Metals. Metallurgy; Nonmetallic coatings; Pitting corrosion; Production techniques; Surface treatment; Pitting corrosion; Aluminium; Filiform corrosion; Surface treatment; Corrosion resistance; Aluminium base alloys; Sheet metal; Paint; Non metal coating; Atmospheric corrosion
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/S0010-938X(03)00003-9

Filiform corrosion of AA 5005 H14 aluminium alloy sheet has been investigated. Painted and scribed panels, with different surface treatments, were inoculated in HCl and exposed in a constant humidity cabinet maintained at 40 °C and 75–85% RH for 1000 h. After exposure, the panels were examined by optical and electron microscopy. It is evident that filiform corrosion susceptibility is determined largely by the near-surface microstructure. Heavily deformed layers, comprising oxide-decorated fine grains and dispersoids on as-rolled and mechanically ground alloy surfaces, are readily susceptible to filiform corrosion. Removal of these deformed layers, by caustic etching and acid cleaning, results in a high filiform corrosion resistance. On such surfaces, underfilm corrosion progresses by localized corrosion of the substrate; with comparatively slowly growing filaments propagating by repeated blistering of the overlying lacquer.