The so-called coating refers to applying protective or decorative coverings to metal and non-metal surfaces. It is an important part of the surface manufacturing process of construction machinery products. The quality of anti-rust and anti-corrosion coatings is essential to ensuring the overall quality of the product. Product appearance and quality not only demonstrate the protective & decorative performance of the product, but also constitute an important factor of the product value.
Generally, mechanical anti-rust coating techniques can be divided into pre-coating surface treatment techniques and anti-rust primer coating techniques.
1. Surface treatment
Surface treatment is one of the important step of the anti-rust coating process. The quality of the anti-rust coating of construction machinery depends largely on the quality of surface treatment.
Mechanical cleaning can effectively remove the rust, welding slag and oxide scale of construction machinery parts, and eliminate welding stress. It also can increase the bonding strength between the anti-rust coating film and metal matrix, thus greatly improving the anti-rust performance of construction machinery parts.
In general, sheet metal stamping adopts the process of chemical surface treatment, including:
Pre-treatment → Hot rinse → Pre-degreasing → Degreasing → Preliminary industrial rinse → Secondary industrial rinse → Surface conditioning → Phosphating →Tertiary industrial rinse → Quaternary industrial rinse → Preliminary pure water rinse → Secondary water rinse → Dewatering → Drying
2. Coating techniques
Generally, the coating is carried out through spraying since the construction machinery is heavy and features various specifications and large spare parts. Spraying tools include air spray gun, high-pressure airless spray gun, air-assisted spray gun and portable electrostatic spray gun. And the coating machinery generally adopts a more advanced water spray chamber.
Small and medium-sized parts can also use a water curtain spray booth and pump-free spray chamber for coating, as the former has advanced performance while the latter is economical, convenient and practical. Since construction machinery features heavy parts and high thermal capacity, the drying of anti-rust coating generally adopts the method of air convection.