Electroless nickel plating uses a chemical reaction instead of an electric current to deposit nickel evenly on any surface, including non-conductive materials. Pre-treatment is crucial and the process faithfully reproduces imperfections. Disadvantages include environmental waste treatment costs and monitoring nickel ion levels. However, electroless nickel plating provides good rust and corrosion protection and can restore old parts.
Electroless nickel plating is an alternative to electroplating which does not rely on an electric current. Both methods use a chemical bath; electroplating passes electricity through the bath and into the workpiece to accomplish the plating, while chemical plating relies on a chemical reaction. Electroplating deposits a layer of the plated material on the workpiece in uneven thicknesses, depending on the contours of the workpiece and the position of the anodes which discharge the electric current into the plating solution. Electroless nickel plating deposits nickel in a uniform thickness throughout the piece, regardless of its geometry. Additionally, electroless nickel plating can deposit the plate on non-conductive surfaces such as plastic, nylon or rubber, a distinct advantage over electroplating.
The first step in the electroless nickel plating process is the preparation of the piece; as with electroplating, the quality of the final work depends on this preparation. The piece must be absolutely free of contaminants or dirt. Even light traces of oil left by human fingers will interfere with the plating process. The pre-treatment of the workpieces takes place through a series of washings with caustic compounds which will effectively remove the surface. After each pre-treatment bath, the piece is thoroughly rinsed with water to remove any residues of the chemical. The final stage of the pretreatment process for conductive pieces is an acid bath to remove any scale; proprietary methods are used for the final pre-treatment steps of non-conductive materials.
After pre-treatment, the pieces are immersed in a chemical bath containing nickel ions and a reducing agent, which causes nickel deposits to form on the piece. Unlike electroplating, nickel plating layers pieces evenly, no matter how irregular its contours. Like electroplating, the electroless nickel plating process will faithfully follow the contours and imperfections of the piece’s surface. If there are scratches in the workpiece after pretreatment, nickel plating will reproduce those scratches. Likewise, any designs, emblems, or text etched into the piece will be reproduced perfectly in a chemical plating job, unlike electroplating, which will likely leave the deepest parts of the grooves and etchings unplated.
Chemical plating also has some disadvantages, usually involving the chemicals used in both the pretreatment and the plating bath itself. Environmentally responsible waste treatment can add significant costs to the chemical plating process. Also, while it is not necessary to monitor an electrical current and keep the bath heated and agitated, it is necessary to monitor the level of nickel ions in the bath and replenish them as they decrease. Even so, electroless nickel plating compares very well to electroless nickel plating, producing a hard, lustrous plate of uniform thickness whose hardness can be increased with appropriate heat treatments. It provides good rust and corrosion protection, often better than electroplating because it is less porous. Electroless nickel plating can also be used to restore old parts by adding thickness to them and then machining them to the correct thickness.
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