Hubei Benxin Environmental Protection Technology Co., Ltd.  |  Tel: +86 27-59835380  |  Mobile: +86 130-1800-6648

Acid Pickling & Chemical Cleaning Inhibitor Applications

Steel pickling & derusting · Boiler / heat-exchanger chemical cleaning · Imidazoline inhibitor solution, recommended dosage 0.1-0.5%

Corrosion Problems During Acid Pickling

Steel pickling (derusting, descaling) and chemical cleaning of boilers and heat exchangers use strong acid media such as hydrochloric or sulfuric acid. While the acid dissolves rust and scale, it also attacks the exposed metal substrate, causing several problems:

  • ⚠️ Substrate over-corrosion: once the rust layer dissolves, the acid attacks the base metal directly, causing surface roughening, pitting, and dimensional deviation on precision parts
  • ⚠️ Hydrogen embrittlement risk: cathodic hydrogen evolution during pickling lets hydrogen atoms diffuse into the steel, and high-strength steel may suffer delayed cracking
  • ⚠️ Acid consumption and fumes: acid reacting with the substrate wastes acid and generates heavy fumes, worsening working conditions
  • ⚠️ Flash rusting after cleaning: the freshly activated metal surface rusts very easily during rinsing and transfer

Imidazoline Acid Pickling Inhibitor Solution

In acidic media, imidazoline molecules protonate into cations that adsorb firmly onto the metal surface through electrostatic attraction and coordination via the nitrogen-containing heterocycle, forming a dense protective film — selectively inhibiting acid attack on the metal substrate while barely hindering dissolution of the rust or scale layer, which is exactly the desired property of a pickling inhibitor.

ItemRecommendation
Recommended productBXH-101 Water-Soluble Imidazoline Polyoxyethylene Ether (active content ≥98%, soluble in water and alcohol)
Recommended dosage0.1-0.5% of the pickling solution volume
Applicable acidsHydrochloric acid (preferred), sulfuric acid, citric acid and other chemical cleaning systems (bench test recommended)
Dosing methodAdd with dilution water while preparing the acid solution and mix evenly before pickling
System advantageFree of Cl, P and metal ions, introduces no additional corrosive impurities

For in-process rust protection after pickling, a rust-preventive oil blended with BXH-102 Oil-Soluble Imidazoline (0.3-1%) can be applied by dip-coating.

FAQ

Q: How much acid pickling corrosion inhibitor should I dose?
The recommended dosage for imidazoline-type acid pickling inhibitors is 0.1-0.5% of the acid solution volume. Use the higher end for high acid concentration, high temperature, or long pickling times. Before scaling up, run a bench test: compare weight-loss coupons in the actual acid with the same material to confirm the inhibition efficiency meets requirements before production use.
Q: Can the same inhibitor be used for both hydrochloric and sulfuric acid pickling?
Imidazoline-type inhibitors perform better in hydrochloric acid systems; adsorption is somewhat weaker in sulfuric acid, so dosage can be increased, or the inhibitor can be blended with synergists such as alkynol or quaternary ammonium salts. Inhibition behavior varies significantly with acid type, concentration and temperature, so we recommend a bench evaluation under your actual pickling process before finalizing the formulation.
Q: Can it reduce hydrogen embrittlement?
Yes, significantly. The imidazoline adsorption film also suppresses the cathodic hydrogen evolution reaction, reducing the amount of hydrogen generated at the steel surface and diffusing into the substrate, thereby lowering embrittlement risk. For hydrogen-embrittlement-sensitive materials such as high-strength steel, pickling time and temperature should still be controlled, and post-pickling hydrogen baking should be applied per specification when needed.
Q: Can it be used for chemical cleaning of boilers and heat exchangers?
Yes. Imidazoline inhibitors are suitable for common chemical cleaning media such as hydrochloric acid and citric acid, at the same dosage as pickling/derusting (0.1-0.5%). After cleaning, rinsing, neutralizing and passivating should be carried out per chemical cleaning practice to prevent flash rusting of the freshly cleaned metal surface.

Request a Free Sample Evaluation

Tell us your pickling process (acid type, concentration, temperature, material) and we will provide dosage recommendations and send samples.

Request Sample Now

Recommended Products

Related Applications