APPENDIX G - GUIDANCE ON VISUAL INSPECTION AFTER ANODISING (NORMATIVE)

Anodic treatment may accentuate the effect of any lack of homogeneity or differences in metallurgical condition of the aluminium. As a result, some non-uniformity of appearance may be encountered on different areas of a component and/or between different batches of material of the same specification, or where certain welding processes have been used.

With colour anodising in particular, the metal composition, form and surface texture, as well as the viewing angle, can have a profound effect on the subjective impression of colour. Co-operation between the metal supplier, the Anodiser and the purchaser is necessary to keep variations within acceptable limits.

It is also possible, on close inspection or from certain viewing angles, to observe variations in brightness, banding, streaking and other visual effects on the significant surfaces. These variations seldom impair the performance of the anodised coating.

It is important that the viewing distance be agreed to; for example, a distance of not less than two metres is required when viewing external architectural applications.

The samples to be used as colour, brightness and die line standards should, if possible, be duplicates of production components or, otherwise, be similarly shaped in order to facilitate comparisons with production components.

Anodised finishes are preferably matched in daylight, but not in direct sunlight.