Surface Finishing - The Hong Kong Polytechnic University

Surface Finishing1. Lifespan of chemicals is limited.2. Waste treatment cost is high due to the speedy chemical renewal.Each type of electroless nickel also has particular advantages depending on theapplication and type of nickel alloyApplicationsIt is commonly used in engineering coating applications where wear resistance,hardness and corrosion protection are required. Applications include oil fieldvalves, rotors, drive shafts, paper handling equipment, fuel rails, and opticalsurfaces for diamond turning, electrical/mechanical tools and office equipment. Itis also commonly used as a coating in electronics PCB manufacturing, typicallywith an overlay of gold to prevent corrosion. Coatings of 25 to 100 micrometrescan be applied and machined back to final dimensions. Its uniform depositionprofile mean it can be applied to complex components not readily suited toother hard wearing coatings like hard chromium.Its use in the automotive industry for wear resistance has increased significantly,however it is important to recognize that only End of Life Vehicles Directive orRoHS compliant process types (free from heavy metal stabilizers) may be usedfor these applications.Bath composition and operating conditionsNickel5.5-6.5g/lSodium Hypophosphite 25-35/lpH 4.2-5.2Temperature85-95°CAgitationmild airDeposition rate 15-25 micron meters/hrPage 41IC Professional Training