Etching aluminum in sodium hydroxide is by far the most common pretreatment for aluminum that is to be anodized. It imparts a matte finish to the end product.
Alkaline etches are also used to strip off anodic coatings. However, under no circumstances should an etch-only finish be used in a finish product because there is no way to prevent the rapid onset of corrosion.
An etch-only finish normally is regarded as an unsightly mess by our customers. It must be anodized immediately upon etching to preserve the uniformly satin appearance imparted by the etch.