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Acid to remove rust from distillation unit

We are trying to remove rust from a distillation unit made of iron. Have tried phosphoric acid, oxalic acid. but the rust keeps coming out. The distillation is for the purification of acids.the temp will be 120 °C.

Uzma [last name deleted for privacy by Editor]
lab testing - Lahore, Punjab, Pakistan
2004

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Dear Uzma,

Have you tried Nitric Acid?

Ijaz Hussain
- Faisalabad
2004

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WHOAAAAAA! If you add nitric acid to anything that has rust, then iron is present. Mixing iron and nitric acid is LETHAL combination! Don't do that please! You'll end up seriously injuring or killing somebody. Hope it's not too late.

Daryl Spindler, CEF
decorative nickel-chrome plating - Greenbrier, Tennessee
2004

You can try hot etching method. In this, about 50 :50 solution is made up of con. HCl acid and water and heated to about 60 deg. C temperature. Scrubbing with this solution after little soaking can remove the rust easily.

RAJESH G. CHANDAVALE
- Pune, Maharashtra, India.
2004