Introduction to the Process of Automotive Painting Production Lines
Release time:
2013-01-30
Huicong Surface Treatment Network: The coating process for automotive painting lines can generally be divided into two major parts: first, the surface treatment of metals prior to coating, also known as pretreatment technology; and second, the actual coating application process. Surface treatment primarily involves removing oil stains, dust, rust, and old paint layers during repair work from the workpiece surface, thereby improving the surface condition of the workpiece. This includes mechanical and chemical treatments applied to the workpiece surface according to specific conditions, such as phosphating, oxidation, and passivation treatments. Automotive Painting Lines—The anti-rust coating process for construction machinery typically consists of two stages: the surface treatment process prior to coating and the application of an anti-rust primer. Surface treatment is one of the critical steps in anti-rust coating. The quality of anti-rust coating for construction machinery largely depends on the effectiveness of the surface treatment method used. According to Imperial Chemical Industries in the UK, the lifespan of a coating is influenced by three main factors: surface treatment accounts for 60%; coating application accounts for 25%; and the quality of the coating material itself accounts for 15%. In the construction machinery industry, different components require different surface treatment methods. Mechanical cleaning can effectively remove rust, weld spatter, and oxide scale from workpieces, relieve welding stresses, and enhance the adhesion between the anti-rust coating and the metal substrate, thereby significantly improving the anti-rust performance of construction machinery components. The standard for mechanical cleaning requires reaching Sa2.5 grade. The surface roughness should reach one-third of the thickness of the anti-rust coating. The steel shot used in blasting and shot peening must meet the requirements of GB6484. For thin-sheet stamped parts, chemical surface treatment is commonly employed. Automotive Painting Lines—The typical process flow is as follows: pre-degreasing → degreasing → hot water wash → cold water wash → acid pickling → cold water wash → neutralization → cold water wash → surface conditioning → phosphating → cold water wash → hot water wash → pure water wash → drying. This process can be adjusted appropriately based on the oil and rust conditions of thin-sheet stamped parts—for example, the acid pickling step may be omitted, or the pre-degreasing step may be skipped. Degreasing and phosphating are key steps in the chemical treatment process, directly affecting both the quality of the chemical treatment and the quality of the anti-rust coating. Relevant process parameters and associated auxiliary equipment are also important factors that cannot be overlooked when it comes to surface treatment quality. Due to the wide range of construction machinery, diverse specifications, heavy overall weight, and large component sizes, spray coating is generally adopted for the coating process. Automotive Painting Lines—Spray coating tools include air spray guns, high-pressure airless spray guns, air-assisted spray guns, and portable electrostatic spray guns. Air spray guns have low spraying efficiency (around 30%), while high-pressure airless spray guns waste coating material. Both types share the common drawback of causing significant environmental pollution, so they have been—and continue to be—gradually replaced by air-assisted spray guns and portable electrostatic spray guns. For instance, the well-known construction machinery company Caterpillar Inc. in the U.S. uses air-assisted spray guns for coating, while portable electrostatic spray guns are employed for thin-sheet coverings such as engine hoods. Coating equipment for construction machinery generally utilizes relatively modern water-spray booths. Small and medium-sized components can also use water curtain booths or pump-less spray booths; the former offer advanced performance, while the latter are cost-effective and convenient. Given the heavy weight and large thermal capacity of construction machinery units and components, the drying of anti-rust coatings typically employs uniform hot-air convection drying. The heat source can be selected based on local conditions, including steam, electricity, light diesel oil, natural gas, and liquefied petroleum gas.
Huicong Surface Treatment Network: The coating process for automotive painting lines generally falls into two main categories: first, the surface treatment of metals prior to coating—also known as pretreatment technology—and second, the actual application techniques for the coating itself. Surface treatment primarily involves removing oil stains, dust, rust, and old paint layers from the workpiece surface during repair operations, thereby improving the surface condition of the workpiece. This includes mechanical and chemical treatments applied to the workpiece surface according to specific conditions, such as phosphating, oxidation, and passivation treatments.
Automotive painting production line
The anti-rust coating process for construction machinery generally consists of two main stages: surface preparation prior to coating and application of an anti-rust primer.
Surface treatment is one of the crucial processes in rust-preventive coating. The quality of rust-preventive coating for construction machinery largely depends on the effectiveness of the surface treatment method employed. According to Imperial Chemical Industries Ltd. in the UK, the service life of a coating is constrained by three key factors:
Surface treatment accounts for 60%; coating application accounts for 25%; and the quality of the coating itself accounts for 15%. In the construction machinery industry, different components employ different surface treatment methods.
Mechanical cleaning can effectively remove rust, weld slag, and oxide scale from workpieces, relieve welding stresses, and enhance the adhesion between the anti-rust coating and the metal substrate.
This significantly improves the rust-prevention quality of construction machinery parts. The mechanical cleaning standard requires reaching a Sa2.5 grade. The surface roughness must be one-third of the thickness of the rust-preventive coating. The steel shot used for blasting and shot peening must meet the requirements of GB6484.
Requirement: Surface treatment for thin-plate stamped parts generally employs chemical surface treatment.
Automotive painting production line
The process flow is as follows: Pre-degreasing → Degreasing → Hot-water washing → Cold-water washing → Acid pickling → Cold-water washing → Neutralization → Cold-water washing → Surface conditioning → Phosphating → Cold-water washing → Hot-water washing → Pure water washing → Drying
The above-mentioned process can also be adjusted appropriately according to the oil and rust conditions of the thin-sheet stamped parts—for example, the pickling step may be omitted, or the pre-degreasing step may be skipped. However, degreasing and phosphating are critical steps in the chemical treatment process.
These two processes directly affect the quality of the workpiece’s chemical treatment and the quality of the rust-preventive coating. Process parameters and related auxiliary equipment are also crucial factors that cannot be overlooked when it comes to surface treatment quality. Given the wide range, numerous specifications, heavy weight of complete machines, and large size of components in construction machinery,
Generally, spray coating is used for application.
Automotive painting production line
Spraying tools include air spray guns, high-pressure airless spray guns, air-assisted spray guns, and portable electrostatic spray guns. Air spray guns have low spraying efficiency (around 30%), while high-pressure airless spray guns result in wastage of paint.
The common characteristic of both is that environmental pollution is relatively severe.
Therefore, they have already been—and are currently being—replaced by air-assisted spray guns and portable electrostatic spray guns. For example, the renowned construction machinery company Caterpillar Inc. of the United States employs air-assisted spray guns for coating applications.
For thin-sheet coverings such as engine hoods, handheld electrostatic spray guns are used. Coating equipment for construction machinery generally employs relatively new water-spray booths. For small and medium-sized components, water curtain spray booths or pump-free spray booths can also be used; the former boasts advanced performance.
The latter is cost-effective and convenient to use. Since construction machinery—both the complete machines and their components—is relatively heavy and has a large thermal capacity, the drying of its rust-preventive coatings...
Generally, a drying method using evenly heated hot-air convection is employed. The heat source can be selected based on local conditions and may include steam, electricity, light diesel oil, natural gas, and liquefied petroleum gas.
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