Agitation

Agitation of parts and solution is necessary during electroless nickel plating to provide a fresh supply of solution to the part and to remove the hydrogen produced during deposition. Without consistent renewal of plating solution, localized depleted areas can occur, resulting in nonuniform coating thickness. Hydrogen bubbles, if allowed to remain on the surface of the part, tend to mask plating and can cause pitting or fisheyes in the coating.

Agitation is accomplished by moving the part mechanically through the solution, by solution movement (preferably by discharge of solution from a suitable filter and distributed by a sparger throughout the tank), or by bubbling air through the bath to move the solution past the part. A typical air agitation spider is shown in Fig. 21. For air agitation, a clean low-pressure air source, such as is provided by centrifugal blowers, is preferred. High-pressure air from compressors can introduce oil or other contaminants into the bath and affect deposit quality.

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