Different methods of removing the α-Al(Fe,Mn)Si particles from the surface of aluminum alloy 6060 (AA6060 [UNS A96060]) have been studied, with the purpose of finding out whether such pretreatment reduces the susceptibility to filiform corrosion (FFC) of epoxy-coated surfaces. The methods, which included immersion in nitric-fluoric acid (HNO3-HF) as well as potentiostatic etching in chloride solution and nitric acid, respectively, exhibited a high efficiency according to scanning electron microscopic (SEM) observations and cathodic polarization measurements in 0.1-M sodium chloride (NaCl) solution. Removal of the α-Al(Fe,Mn)Si particles from the surface of AA6060 reduced the cathodic activity to a level similar to that measured on an iron-free AA6060 model analogue alloy (AlMg0.5Si0.4). However, while the latter was completely immune against FFC, superficial particle removal treatment did not significantly reduce the FFC susceptibility of AA6060 because filament growth was supported by cathodic activity on freshly exposed particles in the filament tails.

Subject
Scanning electron microscopy, Coating removal, Water, Materials, Substrates, Metal surfaces, Aluminum, Corrosion attacks, Sodium chloride solution, Pretreatment, Oxide surfaces, Immersion, Aluminum alloys
Keywords:
aluminum, filiform corrosion, intermetallic particles, pretreatment
NACE International
2004
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