Equipment for Nonelectrolytic Alloy Plating

Nonelectrolytic alloy plating processes use a variety of chemicals in their formulations. Some of the processes have high pH conditions, whereas others operate in the acid pH range. Still others are corrosive to polyvinylidene fluoride (PVDF) and other plastics. Because of this variability of chemistry a number of different materials are used in making the tanks and piping, including polypropylene, polyethylene, polyvinyl chloride, PVDF, PTFE, and stainless steel.

Nonelectrolytic alloy plating equipment is shown in Fig. 2. The plating solution is removed from the bottom of the tank and circulated through a pump, heat exchanger, and filter and then returned to the plating tank through an agitation manifold. Processes using dispersed particles require special fixturing and manifolds to ensure that the particles are distributed uniformly.

Filtration Process Using Manifold

Fig. 2 Tank system for electroless alloy plating

In Fig. 2, the solution is heated with hot water or steam by a heat exchanger. A double mechanical, water-sealed pump is used to circulate the solution from a trough bottom tank that is constructed from natural, stress-relieved polypropylene and welded with inert gas. The piping is made of PVDF and is fuse welded to ensure years of leak-free service. Automatic equipment is used to add replenishment chemicals to maintain a consistent alloy by reducing variations in the process chemistry. Some processes require constant additions to ensure that the processes remain stable. For process volumes of less than 500 L, small chemical-feed pumps that deliver 10 to 20 L/h should be used. Racks, barrels, and baskets are used in the operations to move the parts through the processes. These items should be made of materials compatible with the system.

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