Chemical Forums

General Forums => Generic Discussion => Topic started by: Lewis on October 09, 2019, 08:50:35 AM

Title: Rust removal with citric acid: black residue
Post by: Lewis on October 09, 2019, 08:50:35 AM
Hello,

I would like to know how to remove the black residue, that remains on the surface of carbon steel after rust removal by treatment with citric acid. Household-typical means and minimal abrasive action would be preferred, although the surface is pitted under the rusted areas.

Thanks,
Lewis
Title: Re: Rust removal with citric acid: black residue
Post by: hollytara on October 14, 2019, 11:36:10 AM
If it is carbon steel, the black may be residual carbon - the citric acid would dissolve the metal but leave behind the carbon. 

The carbon might be removable with hydrogen peroxide - you could either use hydrogen peroxide from the pharmacy, or use something like Clorox2, which has hydrogen peroxide mixed with surfactants. 

If you test it on a small area, usually if the hydrogen peroxide is working you will see bubbles forming.