Mechanical Plating
Mechanical plating can be used to apply zinc, tin or aluminium coatings, either singly or in combination. It is, essentially, a 'cold welding' concept that applies the coating using mechanical energy, at room temperature, without giving any lasting hydrogen embrittlement. The components to be coated are placed into a tumbling barrel containing glass beads, reagents and catalysts, which activate and prepare the surface. The coating to be applied is added, in metallic powder form and glass beads of varying sizes 'cold weld' the coating on to the activated surface of the component. To meet specific torque tension requirements, a lubricant, in powder form, can be added during the plating process. Passivates are then applied, prior to drying the parts. Mechanical zinc can be chromated and may be used as an undercoat to enhance the performance of organic paint systems.
Advantages
• No residual hydrogen embrittlement.
• Uniform coating-galling reduced for threaded components.
• Porous substrates can be coated satisfactorily.
• Ideal for sintered components, which normally require surface preparation to stop ingress of aqueous solutions into pores.
• Cost effective replacement for galvanising, removing problem of threads having to be re-rolled, after coating, to remove
excess build ups.
• Useful for thick coatings, cost effective compared to electroplating, since mechanical plating thickness is essentially
independent of process time.
• It is possible to plate some metal components in a pre-assembled state. Where metal assemblies incorporate plastic
or rubber these are unaffected in the plating process - only the metal is plated. - Less harmful to the environment.
Virtually no metal residues are discarded.
Note:
Mechanically plated parts can suffer from transient embrittlement if used within 6 hours of coating. This phenomenon dissipates completely within 6 hours or after 1 hour de-embrittlement.
Normal size of component coated: Up to 200 mm in length or 0.5 kg in weight. It is not possible to coat large items in this process since they cannot be 'tumbled' in barrels.
