Some methods for preparing aluminum for painting include degreasing, grit abrasion, mechanical abrasion and etching. The ideal method of preparing aluminum for painting depends on the nature of the aluminum substrate, the environment and the expected useful life of the paint. Thorough cleaning of the aluminum surface is a prerequisite for each of these methods.
Grit blasting is the most popular of the four methods. This approach removes corrosion and ensures good paint adhesion. To achieve the best results, use abrasives that do not etch or damage the surface, such as aluminum oxide grit.
Degreasing aluminum removes oils and other contaminants from the surface. After cleaning the aluminum surface, use a solvent and clean pieces of cloth to wipe out the contaminants. Change both materials frequently to avoid redistributing the contaminants. Use clean water after the degreasing to ensure the materials do not leave particles on the aluminum surface.
Mechanical abrasion is similar to grit blasting, but it is energy-intensive and uses abrasive disks. This method is ideal when the objective is to achieve a heavily scored surface profile. The process leaves fine deposits on the aluminum surface that require a vacuum cleaner to remove.
The fourth method, using etching, involves a chemical reaction. While grit blasting involves the use of non-etch abrasives, this method requires the use of reactive substances. The method includes alkaline and acidic etching. Alkaline etching uses a strong soda solution while acidic etching employs acidic cleaners.