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Can the chromic acid dip be omitted from MIL-DTL-13924?
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In a recent Supplier Audit I was auditing for compliance of MIL-DTL-13924 and the supplier stated that they did not complete the Chromic acid dip. They also stated that this is an industry standard as supplementry preservative now takes the place of this part of the specification. My question is what does the Chromic acid dip do for this process, and can it be omitted from the process as this supplier has done?
Jill PringAerospace - Muskegon, Michigan, USA
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I am not familiar with that spec, but if the spec calls for a chromic dip, then it has to be done or have a waiver from the end user. It has nothing to do with logic or better, you cannot certify the process if it does not follow the spec or be waived. The people in charge of the specs are not necessarily sharp. Years ago, the office that put out a change to the cadmium spec was not even aware that acid cad was a possibility, let alone desireable in some cases.
James Watts- Navarre, Florida
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Although it may be an industry standard it is required per the mil-spec. As a general rule we will not perform this as well but with the acknowledgment of our customer.
We do perform the chromic dip for the military jobs processed.
Bill Grayson- San Jose
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Jill,
Are you carrying out the Oxalic acid test? From my experience you will not pass the Oxalic acid test without sealing in the Chromic acid solution.
Before you omit the Chromic acid stage you had better check with your customer. If all of the parts have a further supplementary treatment (other than oiling up) then they may well allow you to omit this stage as it is really only of benefit to parts that are either left bare or are consequently oiled.
Brian TerryWestland Helicopters Ltd - Yeovil, Somerset, UK