Surface finish treatment is forming a surface layer process method on the substrate material surface, which has different mechanical, physical and chemical properties with substrate material. The purpose of surface treatment is to meet the product corrosion resistance, wear resistance, decoration or other special functional requirements.
Depending on the usage, the surface treatment technique may be classified into the following categories.
This method is the use of electrode reaction to form a coating in the workpiece surface. The main methods are:
In the electrolyte solution, the workpiece is the cathode, which can form a coating film on the surface under the action of external current, which called electroplating.
In the electrolyte solution, the workpiece is the anode, which can form a anodized layer on the surface under the action of external current, which called anodizing, such as aluminum alloy anodizing.
The anodization of steel can be carried out by chemical or electrochemical methods. Chemical method is put the workpiece into the anodized liquid, it will form a anodized film, such as steel bluing treatment.
This method is using chemical interaction without current to form coating film on the workpiece surface. The mainly methods are:
(A) chemical conversion film treatment
In the electrolyte solution, the workpiece in the absence of external current, by the solution of chemical substances and the workpiece interaction to form a coating on its surface process, known as chemical conversion film treatment.
Because interaction between chemical substances of solution and workpiece without external current which can form coating film on the workpiece surface, which called chemical conversion film. Such as bluing, phosphating, passivating, chromium salt treatment and so on.
(B) Electroless plating
In the electrolyte solution due to the reduction of chemical substances, some substances deposited on the surface of the workpiece to form a coating process, which called electroless plating, such as electroless nickel plating, electroless copper plating.
Thermal processing method
This method is making the material melting or thermal diffusion in the high temperature conditions to form coating film on the surface of the workpiece. The mainly methods are:
(A) Hot dip plating
Put metal parts into the molten metal to form the coating film on the surface of the workpiece, which called hot-dip plating, such as hot-dip galvanizing, hot aluminum and so on.
(B) Thermal spraying
The process of atomizing and spraying the molten metal onto the surface of the workpiece to form a coating film is called thermal spraying, such as thermal spraying of zinc, thermal spraying of aluminum and so on.
(C) Hot stamping
The metal foil heated, pressurized cover the surface of the workpiece to form a coating film process, which called hot stamping, such as hot foil foil and so on.
(D) Chemical heat treatment
Making workpiece contact with chemical and let some elements into the workpiece surface in a high temperature state, which called chemical heat treatment, such as nitriding, carburizing and so on.
Mainly mechanical, chemical, electrochemical, physical method. The main methods are:
(A)Painting coating (B) Strike plating (C) laser surface finish (D) Super-hard film technology (E) Electrophoresis and electrostatic spraying