Influence of metallic ions on chromate-phosphate conversion coatings on aluminium

Abstract
The operating variables encountered industrially when forming conversion coatings on aluminium from chromate-phosphate solutions were studied by scanning electron microscopy, energy dispersive X-ray microanalysis, weight change and potential-time techniques. Increasing quantities of aluminium, magnesium, zinc and copper were added to the solution to simulate ageing. All these additions affected the growth of the coatings, their properties and the proportion of defective coating.