Anodizing aluminum

摘要

Method of anodizing aluminum by subjecting it to electrolysis, first in a bath of electrolyte containing a borate and then in a bath of electrolyte containing an acid. Preferably, the electrolyte in the first bath is about 3-5% borax with the pH adjusted to about 9 to 11 by addition of sodium hydroxide. The method forms an oxide coating which is of sufficient depth to comply with normal specifications and which also does not suffer from alkaline staining.