Anodizing-type surface pretreatment

Resistance of the adhesive joint to salt climates depends not only on the type of adhesive but also on the method of surface preparation and on the type of primer used. The good bond durability in saltwater exposure of anodized surface pretreated joints has been shown... 

Two anodizing surface pretreatments imposed after the acid etching of aluminum have proved to be the best surface for obtaining longest-durability aluminum joints. The pretreatments are referred to based on the type of acid predominant in the respective anodizing baths,... 

Because the morphology of the outer surface of the CAA oxide is strongly dependent on the process steps used just prior to the CAA treatment, the type of pretreatment can be chosen to enhance the bonding. Samples that are FPL-etched and then anodized have a typical FPL shallow cell-and-whisker morphology. Surfaces that are PAA treated before the CAA anodization have a deeper cell structure, typical of PAA. Finally, surfaces that have a smooth tartaric acid-anodized (TAA) oxide before CAA treatment retain a smooth surface which is typical of the TAA treatment. 

The current transients observed upon immersion of n-type Si electrodes in HF of low concentration (2%) depend on the sample pretreatments. Immersion in 50% HF prior to anodization, for example, leads to current densities of up to 30 pA cm-2, which decreases within 1 s to the steady-state dark current value, producing a charge density of 24 pC cnrf 2. This effect has been ascribed to the density of Si-F bonds present on the electrode surface electrode prior to anodization [Be22],... 

The type of surface finish obtained in anodizing depends not only on the process conditions but also on the aluminium alloy concerned (and its pretreat-ment). Whilst a wide range of alloys can be anodized for corrosion protection, fewer can be col our-finished adequately and fewer still provide acceptable bright finishes. Careful selection and handling of aluminium is important, in addition to effective pretreatment. 

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