Mild Steel Countertop Finishing: Architect's questions

The basic problem, either way, is that steel rusts -- almost instantly. When you look at a blued rifle barrel, it is only the oil that keeps it from rusting. Strip the oil and it will flash rust in 15 minutes. So the only way to keep the countertop from rusting is to clear coat it or keep it covered with a thin coat of some kind of wax or oil.

The steel itself poses no hazard; people use rusty frying pans and knives all the time. But what kind of oil, other than food-grade, would be safe?

I think this project justifies a mock-up where you lube a test plate with olive oil^^{mineral oil} and see what happens after you wash it with detergent, cut tomatoes on it, , etc., before committing to building it. An alternative might be color oxided stainless steel.

A. I am planning on doing the same in my home. I have some experience with steel. Mineral oil is non-toxic and often recommended to treat cutting boards, butcher block tables, etc. .
I would not use olive oil ... I question if it will eventually go rancid.

I plan on bluing like you suggested, heat and oil and then coating it with beeswax,.
hand rubbing it or a polisher will do too. It will give a high sheen finish but it will maintain the anti-rust aspect. Yes it will require maintenance but not very often I believe. Good luck!

A. Neither wax nor oil will hold up very long, maybe a matter of days or weeks.

You could use clear polyurethane applied over a scrupulously clean surface. Barring damage from sharp tools, it might last a year or two before needing to be redone.

A. Hi Leslie. The list of proprietary coatings that might "work" is extensive. We have many threads on line here on the general topic of protecting bare steel or rusted steel from ongoing corrosion while preserving the "look", including "How to Rust Steel On Purpose", "Clear coating to seal a rust patina finish on metal", "1001 Q&As on Corten Rusted Steel", "How to accelerate rust on steel" -- and you can search our site for those topics.

But personally I would not put a proprietary product with naptha, stoddard solvent, etc. on a countertop. Good luck.

Regards,

A. What about seasoning the steel? I have a piece of 1/4" plate steel that I seasoned for use as a pizza steel - no rust so far. I used flax seed oil in thin coats on both sides of the steel, placed in my oven at the highest heat level for an hour or two. I did this numerous times, probably nine or ten. Same technique as my carbon steel fry pans.
Might be a problem finding an oven large enough for your purposes though...

A. Hi Susan. There are 101 or more different brands of clearcoats, and we've learned from 31 years of this that unfortunately we can't open the floor on this 'no registration required' forum to claims that the secret ingredients of brand X are better than those of brand Y (why?) -- but we're happy to discuss principals.

The problems you are fighting include both the fact that steel is very rust prone and that proper pretreatment will not be done because you are trying to preserve a raw untreated look, so you won't be phosphatizing, passivating, and priming. It is relatively easy to have a pinhole in any clearcoat whether sprayed or brushed; and in the case of otherwise unprotected rust-prone steel, a pinhole is a bigger problem than on aluminum or on galvanizing or on a prepared and painted surface. So my general suggestion would be two (or more) coats of a relatively thin lacquer, poly, or clearcoat. Everbrite [a finishing.com supporting advertiser] is one respected brand of clearcoat for steel, but I don't claim that there are no others.

Regards,