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Summary of knowledge of material Surface treatment

I. Surface treatment can be divided into the following ways:

  1. Mechanical surface treatment: sandblasting, wire drawing, mechanical polishing, embossing, spraying, shot blasting, polishing, brushing, lacquer, oiling chemical surface treatment: QPQ treatment, nitriding in light, chromization, chromium plating, galvanization, chemical nickel plating, chemical polishing, blackening / bluing, pickling.
  2. Electrochemical surface treatment: anodizing, phosphating, electrochemical nickel plating, electrochemical polishing, electrophoresis. Modern superhardened surface treatment: TD coating treatment, physical vapor deposition (PVD), material chemical vapor deposition (PCVD), chemical vapor deposition (CVD).
  3. Other types of surface treatment: ion plating, ion implantation, laser surface treatment.

II. Description of mechanical surface treatment:

  1. Sandblasting: using the impact of high speed sand flow to clean and coarsening the surface of the parts, the matte pearl silver surface is formed.

Features: improve the fatigue resistance of the workpiece, increase the adhesion between the workpiece and the coating, prolong the durability of the coating, facilitate the leveling and decoration of the coating, and the surface is easy to get dirty.

Application: it can be applied to all ferrous metals and aluminum alloy materials before the table or stainless steel sheet metal surface.

  1. Wire drawing: by grinding the product on the surface of the workpiece to form a thread, to play a decorative effect of the surface treatment, the formation of satin effect. Reflects the texture of metal materials.
  2. Mechanical polishing: using polishing tools and abrasive particles or other polishing media to modify the surface of the workpiece to reduce the surface roughness, to obtain a bright, smooth surface processing.
  3. Embossing: suppress all kinds of texture.
  4. Spraying: covering other non-metallic coatings. Steel sheet metal is often sprayed with color: large wavy white electrostatic spraying, surface powder electrostatic spraying black sub-light, black fine sand electrostatic spraying.

III. Instructions for chemical surface treatment:

  1. QPQ: the purpose of surface modification is to put ferrous metals into two salt baths with different properties and infiltrate into the metal surface through a variety of elements to form a composite infiltration layer.
    Features: good wear resistance and fatigue resistance; good corrosion resistance; small deformation; short time cycle; pollution-free. The error can be kept at 0.005mm.
    Color: bright black.
    Purpose: can be applied to all ferrous metal materials.
  2. Nitriding in light: QPQ upgrade process, steel or stainless steel in the salt bath mixed with a variety of elements for infiltration treatment, can achieve quenching hardness.
    Features: compared with QPQ, it has the advantages of complete non-deformation, higher hardness, deeper depth, higher efficiency and no need for polishing: high nitriding accuracy, non-standard and large parts.
  3. Chromization: trivalent or hexvalent chromized layer is formed on the surface by the interaction of chromium hydrochloric acid solution with metal.
    Features: corrosion resistance, improve the adhesion between parts and organic coating or inorganic coating, good adsorption.
    Color: original color, golden color, green.
    Uses: aluminum, magnesium and their alloys.
  4. Chromium plating: a layer of metal chromium is coated on the surface of the part, the thickness is generally 20um, and the passivation film is formed on the surface.
    Features: high hardness, good wear resistance, high temperature resistance and corrosion resistance. The hardness of hard chromium plating can reach 100OHV. Classification: decorative chromium and hard chromium.
    Color: bright white and blue.
    Application: this process can be used in common steel parts.
  5. Galvanizing: plating a new layer on the surface of metal, alloy or other material to play a beautiful and rust-proof role in the surface treatment, the main method is hot zinc plating.
  6. Electroless nickel plating: also known as non-electrolytic plating, self-catalytic electroplating, nickel deposition. It refers to the process in which metal ions in aqueous solution are reduced by reductant and precipitated into coating on the surface of workpiece under certain conditions.
    Features: uniform coating, strong corrosion resistance, high hardness, high wear resistance, high chemical stability, good adhesion, good weldability, magnetic controllable, high accuracy.
    Color: silver white on the surface is yellowish.
    Uses: all metals (such as steel, stainless steel, aluminum, copper, etc.), non-metals (such as ceramics, glass diamond, carbon sheet, plastic, resin, etc.).
  7. Chemical polishing: the processing of metal surface through regular dissolution to achieve bright and smooth effect.
  8. Black / blue:
    Blackening: the process by which steel or steel parts are heated to an appropriate temperature in air-water vapor or chemical drugs to form a blue or black oxide film on their surface. Iron tetroxide in the outer layer and ferrous oxide in the inner layer.
    Blue: the hair blue film of magnetic iron oxide is obtained by heating steel or steel parts in sodium nitroso and sodium nitrate molten salt or in high temperature hot air and more than 500C °, or in the concentrated caustic sodium of sodium nitroso. The thickness is 0.5-1.5um.
    Features: the corrosion resistance of the blue film alone is poor, which can be improved by applying oil and wax or varnish to improve the corrosion resistance and friction resistance; it has little effect on size and finish, and is often used in high precision parts or standard parts with low cost.
    Color: grayish black, dark black, bright blue.
  9. Pickling: the method of removing oxide scale and rust on iron and steel surface by acid solution is a kind of cleaning metal surface, which is usually carried out with pre-film and is the pretreatment or intermediate treatment of electroplating, Enamel, rolling and other processes.