Protective coatings, grease, oil, mill scale and annealing skin are the most common contaminants found on carbon steel. A surface treatment consisting of degreasing, pickling and phosphating ensures prevention of product contamination, prevention of damage to machinery (blockage of filters, damaging of turbines, explosion danger in pure oxygen systems), prevention of corrosion in specific environments and reduction of flow.
Before pickling, grease, oil, organic contaminants and protective coatings have to be removed by means of a waterbased alkaline product such as Tankclean Alkaline Extra. For spot cleaning local grease, large amounts of oil etc. a hydrocarbon such as Degreaser 156 is used.
To remove oxide layers, annealing skin and mill scale and corrosion products, the material is pickled with inhibited hydrochloric acid or phosphoric acid. The pickling time depends on the nature and thickness of the contamination.
After pickling, the material is internally and externally flushed with a high pressure water jet.
After pickling and flushing with water, flashrust arises immediately. To prevent this, the material is phosphated with a 2-3% hot phosphoric acid solution for several minutes. By doing so, a (temporary) protective layer is created.