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Main methods of corrosion protection for metal drawing parts
- Oct 26, 2018 -

There are several points to be taken lightly in the process of drawing parts: in today's society, stretch parts can be seen everywhere. The process of drawing parts is also varied. Among them, the drawing coefficient is one of the main technological parameters in the production process calculation of drawing parts, which is usually used to determine the order and times of drawing. There are many factors affecting the drawing coefficient m, including the properties of the drawing parts, the relative thickness of the materials, the drawing method (with or without blank holder), the drawing times, the drawing speed, the radius of the punch and die, lubrication, etc.

In addition, in the production process of drawing parts, when the tensile crack occurs, the concave die is coated with lubricant (not in the punch), and the workpiece is coated with 0.013-0.018 mm plastic film on the concave die side.

In the process of drawing, cold work hardening occurs due to cold plastic deformation of the workpiece, which reduces its plasticity, increases its deformation resistance and hardness. In addition, unreasonable die design requires intermediate annealing to soften the metal and restore plasticity. Annealing is usually annealed at low temperature. There are two points to note in annealing: decarbonization and oxidation. After the workpiece is oxidized, the oxide scale will reduce the effective thickness of the workpiece and increase the wear of the die. When the company does not have the conditions, the general use of ordinary annealing, in order to reduce oxide scale production, annealing should be as full as possible furnace. Intermediate annealing procedure should be added when cold hardening metal or tensile cracking occurs in the test mold and there is no other way.

1. Change the internal structure of metal. For example, chromium and nickel are added to ordinary steel to make stainless steel.

2. Cover the metal surface with protective coating. For example, paint on the metal surface, electroplating or chemical method to form compact and corrosion resistant oxide film.

Electrochemical protection. Because metals do not have electrons, the galvanic cell reactions that cause electrochemical corrosion of metals can be eliminated by using the protected metals as the cathode of the reduction reaction in an electrochemical device.

Specific methods are:

A, impressed current cathodic protection. The protected metal is connected with the negative electrode of the power supply by the electrolysis device, and the inert electrode is used as the anode, so long as the applied voltage is strong enough, the protected metal can not be corroded.

B, cathodic protection of sacrificial anode. A new galvanic cell is composed of a protected metal and another metal which is more likely to lose electrons by using a galvanic cell device. When a galvanic cell reaction occurs, the raw metal is used as the positive electrode (i.e. the cathode), which is protected and corroded by an external active metal - the negative electrode (i.e. the anode).

C and corrosion inhibitors can slow down or prevent corrosion of metal parts.