FILIFORM CORROSION OF ALUMINUM SHEET - I - CORROSION BEHAVIOR OF PAINTED MATERIAL

Filiform corrosion (FFC) of cold rolled and painted aluminium substrat es in the AA1000, 3000 and 8000 series, in various tempers and subject ed to various pretreatments, were investigated by use of an accelerate d laboratory test. Modifications in temper from the as-fabricated cond itions were obtained by cold rolling and annealing in the laboratory. As a result of annealing, the surface was activated on alloys AA3005 a nd AA8006, giving rise to severe FFC. By removing or transforming the cuter surface by pretreatment prior to painting, such as by etching or anodising, the FFC resistivity of the annealed substrates was dramati cally improved. The substrates from the AA1000 series were less affect ed by FFC, indicating a smaller effect of annealing. The FFC susceptib ility of the AA1000 series substrates increased with increasing iron c ontent. (C) 1998 Elsevier Science Ltd. All rights reserved