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     Office of Air Quality, Permitting & Enforcement Division

               Mechanical Section Policy Memorandum


Date:  April 19, 1994                          No.: 14   

From:  Skip Clark, P.E. 

Approved by:  Gary Wallin, P.E.

Subject:  Standard Exemption No. 41 Dip Tanks



The standing policy has been that Standard Exemption No. 41
can not be used for any type of chrome plating because the
metal chromium is not listed among the metals in the
exemption.  However, after completing some types of metal
plating operations, it has been the industry standard to dip
the newly coated metal parts into a chromate dip tank for a
final finish.  If the metal parts are not heated prior to the
dip tank, the dip tank is not heated, and there is no current
flow in the dip tank, this dipping action would be allowed
under Standard Exemption No. 41.


Chrome plating has not been allowed under Standard Exemption
No. 41 because of the toxic nature of its emissions.  These
facilities have always required a permit.  In the plating
industry, other than chrome, to achieve a bright finish after
a metal plating operation has been completed, parts are
sometimes dipped into a chromate solution tank.  The chromate
solution gives the part a final brightness.

If the parts are not heated prior to the chromate dip tank,
such as in galvanizing, or if the dip tank is not heated, the
emissions from this operation should be very minor, if any, so
as to not cause, or contribute, to a condition of air
pollution.  Likewise, if there is no current in the dip tank
to produce emissions, just the process of dipping the parts
into the solution should produce insignificant and
unqualifiable emissions.

Therefore, if the above mentioned conditions, as related to
the dip tank, are met, the action of dipping plated parts that
are authorized under the exemption into a chromate solution
for a final brightness finish will be allowed under Standard
Exemption No. 41.

Necessary Action:  None

cc:  All Mechanical Section                    Added 4-20-94