Rinsing

Many processed chemicals are not compatible and may cause contamination if mixed. If your process uses chemicals which are not compatible, rinsing is required between steps  in the process. For example, alkaline cleaners must be thoroughly rinsed before entering acid activation to ensure no solids are formed causing adhesion issues in plating. The main purpose of rinsing between chemical processes is to protect the subsequent chemical process from contamination by the previous chemical process.

Rinsing may also be used as the final step step to remove chemical residues prior to drying. Final rinses, typically high in temperature aid in drying, eliminating the concentration of residual salts improving corrosion protection.

The impact of rinse water usage includes water costs, waste treatment costs and process integrity. Numerous factors have to be considered when determining flow rates of rinses to ensure process integrity and minimization of the costs associated with rinsing.

Good Rinsing Protocols:

• Start with the appropriate tank size. The tank should only be large enough to process the size of the largest part.
• Over-sized tanks require more water, energy and time.
• Water should be introduced to the tank near the bottom.
• Weirs can be used to skim off debris, contaminants and oil and should be located opposite the entry of the water.
• Agitation by air, educators, or pumps is also great practice and helps to keep contaminants from stratifying at the bottom of the tank.

Reduce Water Usage

Counterflow rinsing is a good way to reduce water usage and improve the integrity of the entire process. However, counterflow rinsing has drawbacks including added equipment costs, additional floor space and additional process steps.

Rinsing processes can also be improved  by the use of drag-out rinse tanks. These applications can reduce rinse water usage, as well as serve to improve the process by eliminating large amounts of contaminants being introduced into the rinsing step.

There is no one way or concrete process that works best universally in rinsing. Many factors must be analyzed.