Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Muriatic Acid and Metal
Name: Scott
Status: other
Age: 40s
Location: N/A
Country: N/A
Date: 6/4/2004

I have recently had a new tile kitchen floor cleaned in my home using Muriatic Acid. (That was the builders idea.)The next morning all of the stainless steel appliances were discolored, tarnished and rusty looking. Can anyone tell me the affect the Muriatic Acid fumes have caused with the metal in my kitchen and also what will the long term affects of the metal being exposed to the fumes be?


It's not likely that the stainless was permanently harmed. Just give it a good cleaning with a soft-scrub cleaner made for stainless steel.

ProfHoff 856

Muriatic acid is the "old name" for 30% hydrochloric acid. Usually it isn't necessary or desirable to use it "full strength" to clean a tile floor (It dissolves some of the carbonate minerals in the tile.). Usually "white" vinegar is sufficient to clean the surface of tiles, especially inside a house. And the vapors will discolor even "stainless steel" because the vapors condense on the metal surface with moisture to make more hydorchloric acid. Steel is covered by a thin layer of metal oxides. The hydrochloric acid dissolves and/or etches this layer leaving a tarnished look. It may be difficult to remove that discoloration. As far as the health effects -- the vapors are so irritating that unless someone cannot escape -- they will leave the area before serious damage to the lungs occurs.

Vince Calder

Muriatic acid is just HydroChloric Acid in water, rather concentrated, 30% HCl, 70% H2O . By "tile" I suppose you mean ceramic rather than linoleum? Anyway, HCl evaporates a bit easier than water, and like water it soaks into pores and plastics and takes its sweet time evaporating back out. Its favorite thing in life to do is tickle iron into rust. It doesn't take much to convince iron to rust.

Stainless steel is mostly iron, with fair fractions of nickel and chromium to make an extremely thin skin of tough oxide which stops corrosion in easy cases. With trace quantities of Hydrochloric acid vapors in the air, your kitchen is no longer an easy case. Various grades of stainless steel will resist seawater and HCL fumes for varying lengths of time, from days to months. It appears your stainless is not the most corrosion-resistant grade.

You need to:
- stop accelerating the rust: get your stainless out of there and neutralize acids on it, very soon.

- neutralize acid stuck on/in your kitchen surfaces, floor strongly and cabinets mildly.

- clean up the stainless, which might go into a little time & labor & looking for the best way.

- make a safe place to keep the cleaned stainless so the surface can age in dry air with no cloride or acid fumes pushing it towards rust.

Your kitchen might lose most of its acid vapors in a day to a week, if it gets fresh air, and if there are no cracks or absorbents (wood?) where substantial quantities (milliliters) of the liquid are hiding. If there have been ammonia vapors around, that can make the acid slower to evaporate away. NH3 (vapor) + HCl (vapor) <-> NH4Cl (a solid). Waiting might work, but it's much better to actively neutralize acids after use. It's even considered traditional to do this right after any acid treatment in a vulnerable environment. In your case this doesn't seem to have been done.

To make sure the floor no longer has any acid on or in it, you should mop it with an alkaline or buffering solution. Baking soda (sodium bicarbonate, NaHCO3) in water is safe and probably adequate for this. "TSP" cleaner is more strongly alkaline (anti-acid). I'd try 2 gallons water plus 2 cups baking soda and 1/4 cup TSP, put down and then picked up with a mop, but not rinsed til a week later. (You might not want to put bare feet on it for that time. Don't apply TSP solutions to finished wood. Dilute baking soda solutions are probably OK. If it dries and leaves white streaks or cloudiness on the finish, I'm hoping it's just a little baking soda, and that a couple of water wipes will remove it for good.) Since the acid air got around and maybe settled onto/into wood surfaces, I might wipe all the exposed cabinet surfaces with a dilute baking soda solution, and keep a few tablespoons of the powder on small saucers in each cabinet for a week or more.

With this and the doors closed, your cabinet is now a "safe place", or at least safer than before.

Meanwhile you can attempt to salvage your stainless and keep it in a safer place for a while. I think it can be done without scratching and without leaving much visible evidence of the rust. First I'd try to pry off rust particles with copper-wool potscrubbers or brass brushes from hardware store, soap & water with baking soda, perhaps non-abrasive polish pastes for stainless, or maybe even some oils (to be washed off later). I'd follow that with brief full-strength applications of acidic rust-dissolvers like Naval Jelly or CLR, with immediate copious hot-water rinsing, a baking soda solution dip, a final hot rinse, and drying in an electric oven at about 250-350F (if the handles can take it).

If your stainless has really darkened, tarnished, that's a tougher problem and I know less about what to use for that. Stainless usually looks blue or dark or burned or tarnished from an oxide film grown too thick, and looks better if that can be stripped off. But it's difficult. Maybe a polishing compound for stainless and chrome. There are hot acids that do it, but most people wouldn't want to use them. The talkers at have polished some stainless. Scotch-Brite plastic mesh abrasives on power tools, they've used.

Someone mentioned industrial electro-polishing (big hot acids plus electricity). They warn never to use steel wool or similar, because it leaves embedded bits of iron that rust soon.

Bicycles at my workplace always rust fast, right thru the paint. Stainless breaks out in a while, too. We use lots of acids, but only in the sinks. We presume we have similar traces of acid in our air. Unfortunately it's a poorly enclosed industrial-style space and we can't imagine how to fix it.

Jim Swenson

Click here to return to the Chemistry Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory