19

2018

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06

Why coating/painting is the preferred surface treatment for aluminum wheel?

Author:

Chuangzhi Coating


The general trend of aluminum alloy wheel surface treatment:
 
With the rapid development of the automotive industry, wheel hubs, as key components in automobiles, are increasingly valued for their manufacturing technology. The traditional steel wheels have gradually been replaced by aluminum alloy wheels. In order to make automotive aluminum wheels have a more beautiful appearance, the surface treatment generally uses chrome plating, polishing, painting, powder coating, adding stainless steel or plastic hub caps and improving wheel design patterns. Painting/Coating is the last step in the production of aluminum wheels, and its purpose is to improve the corrosion resistance and aesthetics of aluminum wheels. In order to ensure the quality of painting, the production site requires clean and dust-free. 
 
Aluminum wheel surface treatment is mainly coating, electroplating, etc. In general, there are two major types of electroplating pollutants: First, heavy metals including nickel, cadmium, chromium, and copper, these heavy metals belong to national class of pollutants and are found in electroplating wastewater. Second, cyanide, which is a highly toxic substance. Since the electroplating process has a large impact on the environment, applications are gradually being reduced, and painting/coating has become a dominant process.
 
Aluminum wheel coating/painting process:
 
The coating methods include manual spraying and automatic spraying. The coating thickness and the spraying quality of manual spraying are not easy to control, but, the automatic spraying can control the coating thickness to 10mm and the coating is uniform. Moreover, the coating thickness can be adjusted according to the customer’s requirements. There are two kinds of spray gun, electrostatic spray gun and air spray gun, the latter is only suitable for spray paint.
 
The advanced aluminum wheel automatic coating line is composed of surface pretreatment, drying, electrostatic powder coating, spray painting, curing, etc. The conveyor system includes overhead conveyor system and ground conveyor system. In addition, the coating line is also equipped with transfer robots, powder recovery system, waste gas treatment equipment and wastewater treatment equipment. In the automatic coating process, the electrostatic spray gun technology, high-speed electrostatic rotary cup spray gun technology, non-chrome pretreating technology, powder spray technology and water-base paint technology were selected. As the automatic coating line has the advantages of high production efficiency, environmental protection, and saving coatings, it has become a new trend in the development of aluminum wheel coating technology.
 
Aluminum wheel coating technological process:
 
Pretreatment line process:
Loading→Hot Rinse→Pre-degreasing→Degreasing→Rinse 1→Rinse 2→Acid picking→Spray treatment 1→Pure water rinse 1→Pure water rinse 2→Chromate-free passivation→Spray treatment 2→ Pure water rinse 3→Pure water rinse 4→Sealing→Spray treatment 3→Pure water rinse 5→Direct spray& direct drain→Blow-off→Drip-off→Drying oven→Cooling→Unloading
 
Primer powder coating line process:
Loading→Electrostatic dust removing→Powder coating→Transferring by robot→Fixture cleaning→Curing→Cooling→Transferring by robot
 
Spray painting line process:
Loading→Online grinding→Dedusting→Preheating→Primer painting→Flash-off→Top-coat painting→Flash-off→Varnish painting→Flash-off→Curing→Cooling→Checking→Unloading

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