This cleaning method utilizes the chemical reactions of organic and inorganic chemicals to dissolve and remove soiling on metal materials.

1) The subject soils are the acid/alkali soluble type as follows.

1. Oxidation scales resulting from high temperature processes.
2. Rust removal as a pre-process for metal surface treatment.
3. Pre and post cleaning processes for welding, soldering and brazing.
4. Coating removal of passivated aluminum, magnesium and stainless steel.
5. Burr and metal chip removal.
6. Sludge and hard water scale removal of boilers and heat exchangers.

2) Acids and salts used

1. Acids:
   The acids react with oxides and sulfides turning them into water soluble salts. Sulfuric acid, hydrochloric acid, nitric acid and chromic acid are used. In order to promote moisturizing, foaming and to prevent Corrosions add surface active agent
2. Alkali:
   Alkaline rust removers such as gluconic acid, citric acid, thioglycolic acid salt, ethylenediaminetetraacetic acid (EDTA), and etc. containing chloride complexing agents.
3. Methods
   Since the process relies on chemical reactions, the agents are used in various water solution forms in submerged, sprayed ([Fig.1]), tumbled (in barrels), electrolytic cleaned (anodic/cathodic electrolysis), wiped on, ultrasonic cleaned (ultrasonic vibrations used while submerged), and etc. In order to accelerate the chemical reactions, the solutions are heated (to 40~60°C).
4. Characteristics
   
   1. Alkali cleaning and anodic electrolysis cleaning do not cause hydrogen embrittlement.
   2. Less metal losses compared to sand blasting.
   3. Widely applied as pre-processes for surface treating.
   4. In order to prevent excessive metal dissolution, addition of corrosion inhibitors is required.