Plating method
Electroplating is divided into hanging plating, rolling plating, continuous plating and brush plating and other methods, mainly related to the size and batch of parts to be plated. Hanging plating is suitable for general size products, such as car bumpers, bicycle handlebars, etc. Roller plating is suitable for small parts, fasteners, washers, pins, etc. Continuous plating is suitable for mass production of wire and strip. Brush plating is suitable for local plating or repair. The plating solution has acidic, alkaline and acidic and neutral solutions with chromium mixture, no matter what plating method is used, the plating bath and hanger in contact with the product to be plated and the plating solution should have a certain degree of universality.
Classification of coating
According to the composition of the coating, it can be divided into single metal coating, alloy coating and composite coating.
If classified by use, it can be divided into:
① protective coating;
② protective decorative coating;
③ Decorative coating;
④ repair coating;
⑤ Functional coating
• Single metal plating
Single metal electroplating has a history of more than 170 years, and 33 metals on the periodic table can be electrodeposited from aqueous solutions. Commonly used are electrogalvanizing, nickel, chromium, copper, tin, iron, cobalt, cadmium, lead, gold, silver and other l0 kinds. The alloy coating is formed when two or more elements are deposited on the cathode at the same time. The alloy coating has the microstructure and properties that a single metal coating does not have, such as amorphous Ni-P alloy, each sn alloy that is not on the phase diagram, and the alloy coating with special decorative appearance, especially high corrosion resistance and excellent weldability and magnetism.
• Composite plating
Composite plating is the process of adding solid particles to the plating solution and co-deposition with metal or alloy to form a metal-based surface composite material to meet special application requirements. According to the classification of electrochemical properties between the coating and the base metal, the electroplating can be divided into two categories: anodic coating and negative polar coating. When the potential of the coated metal relative to the base metal is negative, the coating is the anode when the corrosion micro-battery is formed, so it is called the anodic coating, such as the galvanized layer on steel parts; The potential of the coated metal relative to the base metal is positive, and the coating is the cathode when the corrosion micro-battery is formed, so it is called the cathode polar coating, such as the nickel plating and tin plating on the steel parts.
• Classification by use can be divided into:
① Protective coating: such as Zn, Ni, Cd, Sn and CD-SN coating, as anti-corrosion coating resistant to atmosphere and various corrosion environments;
② Protection. Decorative coating: such as Cu-Ni-Cr, Ni-Fe-Cr composite coating, etc., both decorative and protective;
③ Decorative coating: such as Au, Ag and Cu. Sun imitation gold plating, black chromium, black nickel plating, etc.;
④ Repairable coating: such as electroplating Ni, Cr, Fe layer to repair some high cost easy to wear parts or processing out-of-tolerance parts;
⑤ Functional coating: such as Ag, Au and other conductive coating; Ni-Fe, Fe-Co, Ni-Co and other magnetic conductive coating; Cr, Pt-Ru and other high temperature anti-oxidation coating; Ag, Cr and other reflective coating; Black chromium, black nickel and other anti-reflective coating; Hard chromium, Ni.SiC and other wear-resistant coating; Ni.VIEE, Ni.C (graphite) anti-wear coating, etc.; Pb, Cu, Sn, Ag and other weldable coatings; Anti-carburizing Cu plating, etc.
