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.

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.

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

Good luck!