Grain refining etch on aluminum

 

I need an effective method of etching 6061 aluminum to produce a dull matte finish without exposing the pronounced large grain structure. I currently use a caustic etch. I have tried lowering the bath temperature and one proprietary grain refining additive without the desired results. I will subsequently black anodize the part.

You can vary the caustic, carbonate, and simple and complex phosphates to vary the etch.

Then you can try acid etchants containing fluorides will produce a satin etch on some alloys.

Perhaps even a chemical polishing solution may change the look of the surface. One based on phosphoric acid, nitric, acetic, etc.

Best wishes,