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Black dye for hard coat anodized forgings

We are trying to hard coat anodize aluminum forgings and then finish them with black dye. We are having difficulty getting the dye to take in a true black shade. It always seems to come out slightly lighter more like a metallic gray. We are wondering if we should be doing a different preclean step or an additional step prior to anodize. Has anyone had experience with forgings and this type of problem. Your advice would be appreciated

Cheryl Bolduc
- Gorham, Maine, USA
2003

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2003

There is no such thing as black dye. It is a blend of several colors. In the case of thin anodic coatings OR the small pores of cold hard coat the blues and grays absorb preferentially.

Raise your hard coat temperature and the pore will be larger and more dye will absorb. If the higher temperature starts to burn, come back to me for a commercial recommendation on a proprietary hard coat additive which will allow you to build thickness at higher temperatures.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina