Hi

I have a commision to make a balcony with a galvanised acid etch black finish. The galvanising is no problem but the acid etch black finish is. How do achive this?

I use cold bluing solution sold by Jax chemicals, the iron steel nickel blackener works almost instantly. It works great on galvanized metal. I use a wax or a clear coat paint on plain steel not sure if you need it with galvanizing but might be a good idea so your finish doesn't rub off with time and handeling.
It's a little expensive and there is a hazardous handeling fee which is the same for a pint and multiple gallons so more is better.