Rust from Muriatic Acid Fumes

We recently cleaned one of our machines using a mixture of hot water and muriatic acid ⇦ on eBay or Amazon [affil link] . We noticed that in our shop metals were rusting. How long will muriatic acid fumes continue to rust steel? Is there anything that can be done to neutralize this ?

Joe

Hi Joe,
The muriatic (hydrochloric) acid vapor is long gone. Residual chloride (from the initial HCl-steel reaction) absorbs humidity and will continue corroding indefinitely. Possible fixes: wash with an alkaline detergent (TSP preferred) solution, then paint or wash with a water-soluble car wax ⇦ on eBay or Amazon [affil link] .

Caveat: If you ever want to paint or plate the material, avoid waxes containing silicones or fluorocarbons.

For future rust removal, use gelled phosphoric acid (e.g., naval jelly ⇦ on eBay or Amazon [affil link] ) per instructions. This leaves a somewhat protective phosphate film suitable for painting. tannic acid ⇦ on eBay or Amazon [affil link] -based rust converter ⇦ on eBay or Amazon [affil link] s are weaker but require much less rinsing.