​Why do precision castings need to be pickled?

Pickling of investment castings is generally a process in which castings are immersed in an acidic solution and used to remove various oxidized substances and rust on the steel surface through chemical reactions. If the pickling is done well, the next passivation process will be much simpler.

The surface of untreated precision castings has many pores, and it will be difficult to handle after chemical reactions with moisture, oxygen and other substances in the air to form complex compounds. Therefore, before pickling, precision castings must be processed by polishing, grinding, sandblasting and other mechanized methods. If it is still difficult to remove those complex chemicals, then you need to use clean water to clean the surface of the casting. This can not only remove dust and other substances on the surface of the casting, but also fill the pores on the surface of the casting to facilitate subsequent cleaning of chemical treatments.