Alternative to hex chromate for brightening

A. Hello Mr. Rich

There may be alternatives worth investigating, like proprietary sulfuric acid - hydrogen peroxide dips. Contact a distributor or manufacturer of plating supplies.

When one uses hexavalent chromate during processing, there are two alternative scenarios. The first is that some of the chromate must stay on the parts, which are then shipped, and people and the environment are exposed to that toxin. An example is the traditional chromate post-treatment applied to zinc plated brackets and hardware. The world is rapidly addressing that problem through end-of-life vehicle standards, etc.

The other scenario is that, although hexavalent chromate was required in the processing of the parts, none remains on the part. An example of this would be chrome plated goods, which can even be safe to eat off of.

I believe the critical issue is whether hexavalent chromate remains on your parts at ship time. To me, shipping parts that have a toxin on them is equivalent to a doctor sending a patient on his way with a virulent contagious disease, whereas ceasing to process parts the best way you know how because there are toxin hazards that must be managed, is equivalent to a dentists refusing to treat a patient with AIDS.

If you determine that there is no hexavalent chromium on your castings, wastewater treatment of hexavalent chromium is really no big deal. There is a reduction step required, where sodium bisulfite is added to the solution to convert the hex chrome to tri chrome, and after that the trivalent is simply precipitated.