Here comes the 'smarter than' part. You would think that just spreading on some muratic acid or vinegar would produce the desired effect. Wrong. Again, we are in a hurry here, time is money and all that. The process of cold rolling steel is itself an issue. The pressure necessary to produce the product seals the metal surface from the quick action we would hope for. Add to that the small amount of oil that is used to keep the cold rolling process running smoothly and you have another layer of protection against the immediate 'ravages of time' effect we are trying to produce.
|New, untreated corrugated steel|
In the past I have used a biodegradable but industrial strength soap to hurry along the etching effects we look for on galvanized metal, but with this material it seemed relatively ineffective. I had heard from others that sand was a key to help abrade the surface to receive the corrosive effects of the acid. First I sprayed the surface with diluted muratic acid, then sprinkled on some sand, and with a medium soft floor broom proceeded to rough up the metal surface. This worked fairly well but I still had to spray on a second coat of acid and do more brushing to get anywhere close to the surface patina I was looking for.
|Prepped with Acid & Sand|
I next tried to use salt instead of sand and/or in conjunction with sand to speed things up. This worked fairly well but the early patina produced by this mix was not particularly attractive. Still not satisfied with the effectiveness of my attempts at instant rust, I went against my stubborn maleness and asked somebody who knows. Barry Stromberger of "The Slag Works" has been working in metal and metal patina for most of his not insignificant years. He had the answer, ferric nitrate: "Just mix with water in the correct proportions and (after the initial roughening of the surface), spray it on and watch it go".
|Perfectly Rusted Wainscot|
This is one time where 'instant gratification' has paid off handsomely.