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Magnesium corrosion with TCP treatment
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Q. I have several magnesium parts (AZ31B) that have a TCP (MIL-DTL-5541F, TYPE II, CLASS 1A, CLEAR). We have found that on some of these parts there is a visible black corrosion of some kind that appears over time.
We need the TCP coating to protect against corrosion of the part as well as to be electrically conductive. The supplier is not sure why this issue is happening. Is anyone familiar with TCP coatings on mag who has solved this issue before?
- Santa Clara CA
April 24, 2024
A. So, what has changed?
If this is the first time you have tried this combination of part and finish, and it's never worked, maybe the spec is wrong or the way the supplier is applying it wrong. MIL-DTL-5541F is an aluminium spec, so it makes me wonder if someone has changed in AZ31B for another alloy, and not changed the finish spec.
If this was previously working, then either the supplier has changed something, or you have. One possibility is that due to the need for electrical conductivity, they have reduced the coating thickness (more of a Class 3), which would reduce corrosion resistance.
- Melbourne, Australia
May 2, 2024
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