Aesthetics specification for machined components with or without coatings

[BOPdesigner]

Recently we received a cast aluminum part which we have specified on our design documentation to have a conductive conversion coating before powder coating. One of the sides of the part (the base) is not powder coated and we rely on this coating for electrical conduction between this part and a ground plate. On this particular batch of parts, it looked as if perhaps the suppliers chemical tanks were contaminated or something as there were discolorations across the face due to the conversion coating. For all purposes the part met the design print but it looked terrible and we didn't want it do get in the hands of our customer. Is anybody aware of some type of aesthetics standard or verbiage that we can callout on our drawings to prevent this? Its not a surface roughness/finish issue, but more of an appearance or perceived quality defect that we would like to avoid.

 

[drawoh]

BOPdesigner,

In general, conversion coatings are not pretty. If a surface is visible and it must look good, you need to anodize or paint. Have you talked to your vendor at all? Maybe that is all that is required.

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JHG