Parts cleaning is essential in many industrial processes, as a prelude to surface finishing or to protect sensitive components. Electroplating is particularly sensitive to part cleanliness, since molecular layers of oil can prevent the coating adhesion.
Cleaning processes include solvent cleaning, hot alkaline detergent cleaning, electro-cleaning, and acid etch. The most common industrial tests for cleanliness of machinery is the water-break test, in which the surface is thoroughly rinsed and vertically held. A quantitative measurement for this parameter is the contact angle. Hydrophobic contaminants such as oils cause the water to bead and break up, allowing the water to drain rapidly. Perfectly clean metal surfaces are hydrophilic and will keep an unbroken sheet of water that does not bead up or drain off.
