Filiform Corrosion on 6000 Series Aluminium: Kinetics and Inhibition Strategies

A.J. Coleman; H.N. McMurray; G. Williams; Andreas Afseth; Geoff M. Scamans

doi:10.4028/www.scientific.net/MSF.519-521.629

Paper Titles

Damage Tolerance Capability of an Al-Cu-Mg-Ag Alloy (2139)
p.603

Influence of an Inclined Cooling Plate on the Production of A356/CNF and A356/SiC MMC by Compocasting
p.609

The Role of Alloying Elements on the Surface Treatment and Finishing of Aluminium
p.615

Surface Science Studies of the Effect of Al Alloy Microstructure on the Formation of Chromate Coatings
p.621

Filiform Corrosion on 6000 Series Aluminium: Kinetics and Inhibition Strategies
p.629

Influence of Composition and Roughness on Localized Corrosion of Al-Mg-Si Alloys Characterized by Microelectrochemistry
p.635

Intergranular Corrosion and Stress Corrosion Cracking of Sensitised AA5182
p.641

Corrosion of Painted Aluminium Sheet
p.647

Fracture Mechanical Testing of Adhesion of Organic Coatings on Aluminium
p.655

HomeMaterials Science ForumMaterials Science Forum Vols. 519-521Filiform Corrosion on 6000 Series Aluminium:...

Filiform Corrosion on 6000 Series Aluminium: Kinetics and Inhibition Strategies

Abstract:

High levels of surface shear experienced during rolling, grinding or machining can cause 6000 series aluminium to develop an ultra-fine grained surface layers which dramatically increase susceptibility to filiform corrosion (FFC) under paint films. In-situ Scanning Kelvin Probe (SKP) measurements in humid air are used to compare the kinetics and mechanism of FFC on abraded and lacquer-coated samples of high copper containing AA6111 and low level copper AA6016. FFC is initiated by applying a small volume of aqueous HCl to a penetrative defect on polyvinylbutyral (PVB) coated alloy samples prior to placement in a chamber maintained at constant humidity and temperature. The SKP is then repeatedly scanned over a fixed surface area to produce a time-lapse animation showing the dynamic evolution of localized free corrosion potential patterns. The spatial distribution of potential variation provides insight into the FFC mechanism and the numerical integration of areas of dissimilar potential provides a measure of the time-dependent area of coating delamination. Various possible FFC inhibition strategies are investigated for use under circumstances where removal of the surface layer prior to application of an organic (paint) coating is not feasible. The two strategies shown in this paper are the use of an anti-corrosion pigments based on an intrinsically conducting polymer called polyaniline. An anion-exchange pigment called hydrotalcite is also used.