Water is an invaluable tool in achieving reliable contamination control and appropriate surface quality. Sometimes, however, water itself is a contaminant.

For critical components or parts, water may be the best approach for removing other soils. Outgassing of lower boiling organic solvents is a concern; however, higher boiling solvents can, like water, be trapped in blind holes or absorbed into plastics or other synthetics.

The consequences of contamination by either water or solvents include corrosion, gradual breakdown of the product during use, and degradation of coatings. If the coating failure is primarily aesthetic, the main consequence will be customer dissatisfaction. If the coating is required for critical surface characteristics, as in biomedical implantables, even if the product is used in an environment which is itself primarily water, residual underlying moisture at the coating stage can shorten product lifetime.

Water can also interact with other fluids found in the completed product. Water can, for example, interact with the flotation fluids used in some gyroscopes. Residual water can be a problem in other areas as well; moisture retained in motion picture film has been associated with the breakdown of master copies of classic movies.

This doesn’t necessarily mean that all water must be removed from all products. In some cases, as in lyophilization, the quantity of water must be controlled, not necessarily minimized to below any imaginable detection limit.