mech15.txt
mech15.txt — 1.9 KB
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Office of Air Quality, Permitting & Enforcement Division Mechanical Section Policy Memorandum Date: May 17, 1994 No.: 15 From: Skip Clark, P.E. Approved by: Gary Wallin, P.E. Subject: Aluminum Anodizing under Standard Exemption No. 41 Policy: The anodizing of aluminum with sulfuric acid only will be allowed under Standard Exemption No. 41. Anodizing aluminum with chromic acid, or any other solutions, will continue to require a permit. Background: Anodizing is defined as the forming of a conversion coating on a metal surface by anodic oxidation, most frequently applied to aluminum. This is to form an oxide layer on the metal to prohibit or restrict additional oxidation or rusting of the metal surface. Previously, the anodizing of aluminum was not allowed under Standard Exemption No. 41 because of the way the exemption was worded. Only those metals listed in the exemption could be anodized. After talking with a number of knowledgeable individuals, it appears that anodizing should have been added to the second part of the sentence where cleaning, stripping, etching, or other surface preparation is allowed. The consultant to the American Electroplaters and Surface Finishers Society said that the emissions from the anodizing of aluminum by sulfuric acid would be very minimum, although he had no emission factor available. Aluminum can also be anodized with chromate acid to not only form the protective layer, but give it a bright finish. This will continue to be prohibited under this exemption. Only sulfuric acid can be used in the anodizing process at this time in order to meet the conditions of this exemption. Necessary Action: To re-write Standard Exemption No. 41 to clarify the process of anodizing. cc: All Mechanical Section Added 5-17-94