Letter 7046

What is inhibited HCl ? 

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We have a very serious scaling problem in our filter tubes, we have tried all sorts of cleaning mechanisms. we have been informed that inhibited hcl would help in descaling. kindly let us know what inhibited hcl is?

sanghani harshal
- nocil-rcd

Straight HCl will attack steel as well as scale and rust. Inhibited HCl has organic additives that tend to coat the cleaned steel to inhibit the attack on the steel.

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

The word "inhibited HCl" is usually used to indicate hydrochloric acid with acid corrosion inhibitor.

Hydochloric acid is usually used as diluted in water, particularly 3 to 10% which varies by the fouling characterisitics and material in the system.

Acid corrosion inhibitor means organic compound which adsorps metal surface to protect metal from acid atmosphere. It is commercially aveirable and typically composed of several mixture of organic amines, imines, and/or thioureas, and so on.

There are a lot of products from chemical companies in the market and several types depend on the applications such as hydrochloric acid, sulfuric acid, organic acids, and so on.

The inhibited acid is at times heated usually up to 60 deg.C to facilitate the desolving reaction between scale and the acids.

You should be careful to apply these acids, because hydrochloric acid, even inhibited, could attack some materials, like highly mechanically arranged devices and could lead to serious damage like cracking or partially detremental corrosion. Especially for austenitic stainless steel, when it is finely modified.

Hiromi Kawaguchi
- Tokyo, Japan

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