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Dulling a galvanized finish

I manufacture steel garden seats that are then hot dip galvanised. Some purchasers do not want the seat to be painted but do not like the shiny finish of galvanizing. What acid should I use to create an even dark grey or black finish to the galvanizing please.

Michael Bulwer Knight
manufacturer of garden seats - Taunton, Somerset, England
2004

In the UK a commonly available and low cost option is "T wash", this is a phosphoric wash used mainly as a preparation for overpainting galvanizing, but could be just left in the black finish it leaves. Zinc is so reactive that you could use almost any acid, but health and safety become prime considerations.

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

2004

You can use 200 gm iron(III) chloride/1 lit water solution, or 5 gm potassium permanganate ⇦ on eBay or Amazon [affil links] /50 gm copper sulphate/1 lit water solution!

Good luck!

Goran Budija
- Cerovski vrh Croatia
2004

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