Letter 12028

Pickling Steel 

I am a student from Strasburg high in Colorado and I was wondering what is pickling steel? I have been looking all over the internet and you are the closest I have gotten.

Thank u,

Luke P
- Strasburg, CO, America

If you picture the making of steel, Luke, you have a red-hot metal that you are forming, rolling, forging, or whatever. The surface of the steel is going to react with the oxygen and water vapor in the air, forming something similar to a very heavy rust. This is called 'scale'. The scale needs to be removed, and 'pickling' is usually the name given to the chemical removal of scale.

Ted Mooney, P.E.  finishing.com Brick, NJ

I want to know the uses and composition of Pickling Inhibitor used in the pre-galvanising proces of cold rolled steel.

Ishaq
Maharashtra Trading Co - Jaipur, India

Hydrochloric acid is used to remove rust and scale from steel, Ishaq. But hydrochloric acid will also attack and dissolve the steel itself. The purpose of a pickling inhibitor is to reduce the attack on the steel. This saves steel, and lengthens the life of the acid.

One way of answering your question about composition is to say it's not a basic generic chemical formulation, it's a proprietary product. Good luck.

Ted Mooney, P.E. 
finishing.com
Brick, NJ

I work for a general contractor and I am reviewing the specifications for metal fabrications. The specs call out pickling before galvanization. I understand a little that pickling is a trade name for a chemical used to remove rust. How exactly is this process done in the factory? Can pickling be done in the field (ie on a job site)?

Sam Johnson
- Cotapaxi, Colorado, USA

"Pickling" is not a tradename, it is an industrial process for removing mill scale. Often there is a mechanical 'scale breaking' step first, which passes the product through rollers designed to fracture the brittle scale to mechanically flake off what you can, and to offer more surface area for quicker chemical reaction. Then hydrochloric or sulfuric acid dissolves and removes the heavy mill scale.

You can field apply some acids to structures if an occasion warrants, but as a semantic issue I don't think people would call this 'pickling'.

Ted Mooney, P.E. 
finishing.com
Brick, NJ

Sir, I am a student carrying out a project work on PERFORMANCES OF VARIOUS PICKLING SOLUTIONS ON RUSTY MILD STEEL. Pls, assist me with the various types of pickling solutions for removing rust on mild steel including there compositions.I will be grateful.thank you

Chris M.
student - Califonia, USA

Phosphoric acid is sold commercially as Rust Converter [link is to product info at Amazon] or Naval Jelly [link is to product info at Amazon], Chris. This is best for deterring future rust. The more powerful acid for quickly dissolving rust is hydrochloric acid, sold commercially as Muriatic Acid [link is to product info at Amazon], but this leaves the surface extremely active and prone to flash rusting. Good luck.

Ted Mooney, P.E. 
finishing.com
Brick, NJ

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