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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



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.


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