This is a method of removing contamination from metal surfaces by the use of detergents made of chemicals and surfactants. The detergents pulls the contaminants from the metal surfaces and keep the contaminants stably suspended within the detergent in order to prevent from being redeposited on the metal.

1)Detergent types

Can be classified generally as follows.

(1)Alkaline salt water solution (caustic soda, sodium carbonate, sodium phosphate, silicate soda, etc. sometimes acidic detergents such as hydrochloric acid and acid/water solution are used) composition example is shown on [Table 1].

[Table 1] Example of alkaline degreasing bath for steel (g/L)

(2)Surfactant solution
(3)Alkaline degreasing solution (solution of alkaline salt and surfactant)
(4)Emulsified degreasing solution (solvent and surfactant)

2) Cleaning method

Functions of the detergents are: replace, solubilize, disperse, emulsify, saponify the contamination. There are following methods but since they all use solutions, they are strongly affected by the solution temperature. The higher the solution temperature, the higher the detergent power.

(1) Immersion, immerse and oscillate (Also called Immersion Cleaning. Work-piece is immersed in degreasing bath)
(2)Spray cleaning (Used when work-pieces are transferred on conveyors)
(3) Tumbling barrel cleaning (Small parts and detergent are placed in a barrel and tumbled)
(4)Steam cleaning (Used for cleaning large objects such as automobile)
(5)Brush cleaning (From hand brushing to automated rotary brush)
(6)Electrolytic cleaning (DC current is used with Immersion Cleaning)
(7)Ultrasonic cleaning (Ultrasonic wave is used with Immersion Cleaning)

3)Characteristic of this method

This method is applicable to all soiling and is suitable for rough cleaning, often used for pre-treatment of electro-plating, anodizing, PVD, CVD processes, as well as pre- and post processes for pickling and mechanical scale removal. The detergents are all low in costs and water rinsing can be used since they are water soluble, safe foe the operators without any risk of flammability or toxicity.