All anodizing processes produce coatings with pores in their surfaces. These pores are necessary for the addition of dyes and printing, as well as for the retention of lubricants. However, they also provide in-roads for corrosion. To eliminate this potential for corrosion, and to lock in printed graphics and dyed colors, anodized coatings can be sealed. Sealing also increases the coatings’ stain resistance. However, sealing will reduce the coatings’ lubricity and abrasion resistance.
A simple method of sealing anodic coatings is prolonged emersion in boiling deionized water or steam. Oxides are converted to their hydrated forms, which results in swelling that reduces the porosity of the anodized surface. This method, though common, is not completely effective. Abrasion resistance can be reduced by as much as 20%.