FACTORS AFFECTING THE ADHESION OF SURFACE COATINGS TO ANODISED ALUMINIUM ALLOYS.
Abstract
An investigation was made of the factors effecting the adhesion of aircraft paint systems to anodised aluminium and aluminium alloys. The equipment used in the chromic and sulphuric acid processes on both plant and laboratory scale is described in detail and analysis figures for the baths and post anodising treatments are detailed. The panel preparation and experimental procedure for the determination of the adhesion of the surface coatings by the direct pull-off sandwich technique are described. The effect of such bath composition variables as age of bath, the presence of inorganic and organic contamination, CrO3 content and type of water, together with the effect of rinsing waters, chromate contamination, sealing temperature, and delay period before application of the paints was studied. The adhesion of the test paint systems was assessed under three conditions of ageing. Inorganic contamination present during post anodising treatments has an adverse effect on paint adhesion, but when present during anodising, does not appear to have any marked effect. Organic contamination present during anodising is also associated with an increase in apparent adhesion failures particularly when etch primers are used. The majority of adhesion failures are associated with the anodic film on L70 alloy especially when phenolic modified etch primer to DTD5555 is used. Micrography showed that cohesional failures in the anodic film can occur and it is believed that this type of failure is the real explanation for many of the apparent adhesion failures. It was concluded that Specification DTD910C does not adequately define the anodising process to ensure reproducible point adhesion on all alloys. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1967
- Accession Number
- AD0660411
Entities
People
- A. R. Popley
- C. A. Terry
- Phillip Walker
Organizations
- Atomic Weapons Establishment