Blackening phenomenon and analysis of excavator cylinder

The surface of the oil cylinder is covered with a colored film

The cylinder will first turn blue, then deepen in color, turn purple, and finally turn black. The blue color is caused by the additives in the oil seal and hydraulic oil adhering to the cylinder rod at high temperatures. The blackening is caused by the lead-containing additive in the spray material in the cup (i.e. wear-resistant sleeve) adhering to the cylinder rod at high temperatures.

Cause of discoloration
1. There is a high temperature phenomenon in the hydraulic system. During work, the piston rod is in high temperature (especially in the cold season) and frequently comes into contact with the low temperature environment (the temperature drops suddenly).
2. When a different brand of hydraulic oil is replaced during the maintenance cycle, this phenomenon will usually cause the piston rod to change color within a few days of changing the oil. The reason is that there is an extreme pressure anti-wear additive in the hydraulic oil that has different qualities and properties.
3. During the electroplating process of the piston rod, uneven temperature control caused cracks to appear on the surface of the electroplated layer in the later work. When observing the surface of the piston rod with a high-power magnifying glass, irregular small cracks can be seen.
4. The blue color is caused by the additives in the oil seal and hydraulic oil adhering to the cylinder rod at high temperatures. The black color is caused by the lead-containing additives in the spray material in the cup (i.e. wear-resistant sleeve) adhering to the cylinder rod at high temperatures. . It is generally caused by the hydraulic oil temperature being too high, and this phenomenon often occurs in the front half of the bucket cylinder that is used more frequently. It is recommended that the dust on the radiator part be cleaned frequently to ensure the heat dissipation effect.

How to deal with the discoloration problem of excavator cylinder?
If there is a very small part of the blue color in the oil cylinder, you can ignore it and it will disappear automatically after a while. If the discoloration is severe, the oil seal and wear-resistant sleeve need to be replaced, and try to avoid high temperatures in the hydraulic oil.

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