Metal Cleaning

Metal cleaning is a key aspect of the metal industry. Phosphates and phosphoric acid from ICL Phosphate Specialties play a critical role in this area.

In order for finishes to be successfully applied in later operations, metal surfaces must first be sufficiently cleaned. Removal of all foreign matter from surfaces prior to painting or other surface preparation is critical for acceptable adhesion. Foreign matter includes grease, oil, particulate matter, corrosion oxides, scale and stencil markings. Effective cleaning is achieved through a combination of detergency, chemical reaction, solvent dissolution and mechanical action. Acid cleaners, formulations with pH lower than neutral (pH 7), are more effective on scale, smut, lime and milkstone.

Alkaline cleaners are more effective in removal of grease, oils and fatty soils, as well as solid soils. Principal methods employed in cleaning metal parts include spray, soak and electrolytic. Our phosphates and phosphoric acids are used extensively in the alkaline and acid cleaners. Alkaline cleaners primarily contain water, builders and surfactants. Builders provide alkalinity and soften the water used in the cleaning process. This includes ICL sodium tripolyphosphate (STPP), tetrasodium pyrophosphate (TSPP), tetrapotassium pyrophosphate (TKPP) and trisodium phosphate (TSP).

Acid cleaners are composed of mineral acids, organic acids or acid salts, in combination with a wetting agent and detergent. Inhibitors and solvents may also be added for specific applications. ICL phosphoric acid, monosodium phosphate (MSP) and sodium acid pyrophosphate (SAPP) are commonly used ingredients in acid cleaning formulations.

Acid pickling refers to a relatively more severe treatment for the removal of scale from semifinished mill products, forgings or castings, whereas cleaning usually refers to final or near-final preparation of metal surfaces prior to plating, painting or storage. Commonly used acids for pickling stainless steels include nitric, sulfuric, hydrochloric and phosphoric. Phosphoric acid/ethylene glycol monobutyl ether mixtures are widely used for cleaning grease, oil, light rust and scale from iron and steel. More detailed information on these and other applications are available from our technical service group.

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Sodium Acid Pyrophosphate (SAPP)

Used in metal treatment and cleaning. Good builder for use in acid cleaners. Can also sequester iron and copper.

Monosodium Phosphate

•Excellent carrier for liquid surfactants and phosphoric acid.

Phosphoric Acid

•Used in aluminum cleaner/brightener formulations
•Major phosphatizing ingredient

Tetrapotassium Pyrophosphate, Tetrasodium Pyrolphosphate

•Builders of choice where high alkalinity and prolonged high temperatures are required, such as soak tank cleaner
•Used as builders in formulations containing caustic to aid in the rinsability of caustic