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RoHS and Chem Treated Steel

In light of the pending Directive, RoHS, does chem treated steel need to be considered?

Is there anything in the Alkaline Cleaner of Iron Phosphate chemicals that need to be changed or contain Hex Chrome, etc.

Rich Kiolbasa
Pentair - Des Plaines, Illinois, USA
2005

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2005

'Chem treated steel' is sufficiently ambiguous that hexavalent chromium could be present.

Hexavalent chromium is not necessary for acid cleaning, neutral cleaning, alkaline cleaning, iron phosphating, zinc phosphating, manganese phosphating, zinc plating, etc., of steel.

BUT
to prevent flash rusting and improve long-term corrosion resistance, processes may include a dilute chromic acid 'sealing rinse.' For many years this was SOP for zinc phosphate used as a paint base. Most zinc plating hitherto has included hex. chromating for corrosion resistance and coloration.

THEREFORE
For RoHS compliance, your process specifications should explicitly prohibit the use of hexavalent chromium in any form. Explicitly require a non-hex. chromium sealing rinse for phosphate coatings. Require trivalent chromate or non-chromium coatings for zinc plating.

Other RoHS's would not be present unless specified, e.g., Cd plating (often chromated, still allowed in critical applications), chromate anti-corrosive paint pigments (still in some MIL & aircraft specs.), lead paint pigments (banned in the US for many years), mercury anti-fungal paint additive (banned ~worldwide).

Galvanized sheet steel has traditionally been quenched (after the hot dipping) in a hex. chromium solution to avoid corrosion. Not sure about current practice. Anyone else know?

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.