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Reapplying Clear Chromate on AL 6061 after post machining


Two questions:

1. Chromated AL 6061 housing and parts used in fiber optic transmitting device (Laser, Receiver, PCB) If I modify a 6061 Aluminum bracket that has a clear chromate finish and the modified surface does not make contact with anything else, any reason why the part needs to have the chromate re-applied.

2. Standard machining process solvents - do they affect the integrity of the chromate finish - i.e. post machining a part already chromated?


Ted Beszterczei
Optium Corporation - Chalfont, Pennsylvania, USA

You may find lots of opinions on this. Generally, if you machine a part after chromate, you have lost the corrosion protection in that area and probably in the clamping area.

Is this ok? We do not know what your needs are--It depends! does cutting fluid hurt? Normally not much, but I will bet a large coffee that somewhere in the world, someone is using one that does. Some hand lotions are wonderful at removing chromate, so why not some cutting fluids? Some customers allow the use of a chromate touch up kit. Not as good as a tank chromate, but a lot better than no chromate.

James Watts
- Navarre, Florida

Thanks for the response. Normally we do re-chromate the parts. This was a situation of parts in production that needed to be modified quickly. Re-chromating the parts would have cost another day or two, so I made the decision to not chromate based on the point that the surface being modified did not make contact with anything else. I did forget the fact that the clamping points may also loose their chromate due to abrasion of clamping tool(thanks). We have had chromate brushed on in the past, but this latest situation did not allow it due to time constraints.

Another related question: As AL 6061 oxidizes I understand I loose conductivity, but what does it physically transform into (i.e. nonconductive powder, conductive flakes, etc)?

Ted Bezterczei
Optium Corp - Chalfont, Pennsylvania

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