what does galvanization mean

Electroplating is the use of electrolytic principle in some metal surface plating on a thin layer of other metal or alloy process, is the use of electrolytic effect of metal or other materials on the surface attached to a layer of metal film process so as to prevent metal oxidation (such as corrosion), improve wear resistance, electrical conductivity, reflective, corrosion resistance (copper sulfate, etc.) and improve the appearance of the role. The outer layer of many coins is also electroplated.

The basic meaning of electroplating

Electroplating, plating metal or other insoluble materials as the anode, the workpiece to be plated as the cathode, plating metal cations on the surface of the workpiece to be plated is reduced to form a coating. In order to eliminate the interference of other cations, and make the coating uniform and firm, it is necessary to use the solution containing metal cations electroplating solution, in order to keep the concentration of metal cations in the coating unchanged. The purpose of electroplating is to coat the substrate with a metal coating to change the surface properties or dimensions of the substrate. Electroplating can enhance the corrosion resistance of the metal (coating metal is mostly corrosion-resistant metal), increase hardness, prevent wear, improve electrical conductivity, smooth, heat resistance and surface appearance.

Classification of electroplating

Electroplating method

Electroplating can be divided into hanging plating, rolling plating, continuous plating and brush plating, which are 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 topical plating or repair. Electroplating solution has acidic, alkaline and chrome mixture of acidic and neutral solutions, no matter what kind of plating method, and to be plated products and plating solution in contact with the plating bath, hanging device, etc., should have a certain degree of versatility.

Coating classification

If the composition of the coating can be divided into a single metal coating, alloy coating and composite coating three types.

If it is 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 kinds of metals on the periodic table can be electrodeposited from aqueous solution. Commonly used are galvanized, nickel, chromium, copper, tin, iron, cobalt, cadmium, lead, gold, silver and so on 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, magnetism, etc.

Composite plating

Composite plating is a process in which solid particles are added to the plating solution and co-deposited with metal or alloy to form a metal-based surface composite material to meet special application requirements. According to the electrochemical properties between the coating and the substrate metal, electrodeposited coatings can be divided into anode coating and cathode coating. Where the coating metal relative to the substrate metal potential is negative, the formation of corrosion microcell coating is anode, so called anodic coating, such as galvanized layer on steel parts; The potential of the coated metal relative to the substrate metal is positive, and the coating is the cathode when the corrosion microcell is formed, so it is called negative polarity coating, such as nickel plating and tin plating on 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 environment;

② Protection. Decorative coating: such as Cu - Ni- Cr, Ni-Fe-Cr composite coating, both decorative, and protective;

③ Decorative coating: such as Au, Ag and Cu. Sun imitation gold coating, black chromium, black nickel coating, etc.;

④ Repair coating: such as plating 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 conductive coatings; Cr, Pt-Ru and other high temperature anti-oxidation coatings; Ag, Cr and other reflective coating; Black chromium, black nickel and other anti-reflective coating; Hard chromium, Ni.SiC and other wear-resisting coatings; Ni. VIEE, Ni. C(graphite) wear reduction coating, etc.; Welding coating of Pb, Cu, Sn, Ag, etc.; Carburized Cu plating, etc.

Material requirement

The coating is mostly single metal or alloy, such as titanium, palladium, zinc, cadmium, gold or brass, bronze, etc. There are also dispersion layers, such as nickel-silicon carbide, nickel-fluorine ink; There are also cladding layers, such as copper - nickel - chromium layer on steel, silver - indium layer on steel, etc. In addition to iron based cast iron, steel and stainless steel, there are also non-iron metals, ABS plastics, polypropylene, polysulfone and phenolic plastics, but before electroplating, plastic must undergo special activation and sensitization treatment.

Related effects of electroplating

The technique of depositing a metal coating on a mechanical product with good adhesion but different properties than the base material using the principle of an electrolytic cell. Electroplating layer than the hot dip layer uniform, generally thinner, from a few microns to dozens of microns. Through electroplating, it is possible to obtain decorative protection and various functional surface layers on mechanical products, and repair worn and machined parts.