Metal air spraying
Metal air spraying is a coating technique that uses compressed air to atomize and spray paint onto metal surfaces. It is widely used in industrial corrosion protection, decoration, and other fields. The core principle is that the high-pressure airflow generated by an air compressor creates a negative pressure at the spray gun nozzle, drawing the paint from the storage tank and breaking it into fine droplets. These droplets, propelled by the airflow, adhere evenly to the metal substrate surface, forming a complete coating after drying or curing. This technique is simple to operate and has relatively low equipment costs. It is suitable for metal workpieces of various shapes and sizes, from small components to large steel structures, and can achieve efficient coating.
Among the process parameters for metal air spraying, air pressure, paint viscosity, and spray gun distance are key factors influencing coating quality. Too little air pressure can lead to insufficient paint atomization, making the coating prone to sagging and uneven thickness. Excessive pressure can cause significant paint rebound, resulting in paint waste, and can also introduce excessive air, causing pinholes or bubbles in the coating. Paint viscosity needs to be adjusted using appropriate diluents. Excessive viscosity makes atomization difficult and can easily crack the coating after drying. Too little viscosity can result in insufficient coating coverage, affecting protective performance. The distance between the spray gun and the workpiece surface is generally controlled between 15-25 cm. Too close a distance can lead to localized paint accumulation, while too far can increase paint loss and reduce coating uniformity.
A wide variety of coatings are used in metal air spraying, including oil-based, water-based, and powder coatings. Different types of coatings are suitable for different working environments and performance requirements. Oil-based coatings offer excellent adhesion and weather resistance, but they are high in volatile organic compounds (VOCs), which can pollute the environment. Water-based coatings, which use water as a solvent, offer excellent environmental performance, but they dry more slowly and require a high humidity and temperature range for the application environment. Powder coatings adhere to metal surfaces through electrostatic adsorption and cure at high temperatures to form a coating. They are solvent-free, offer uniform coating thickness, and exhibit strong corrosion resistance. In recent years, they have experienced rapid growth in areas with stringent environmental requirements.
In practical applications, metal air spraying requires preliminary surface treatment, which is directly related to the adhesion and service life of the coating. Impurities such as oil, rust, and scale on the metal surface must be thoroughly removed. Common treatment methods include mechanical grinding, chemical rust removal, and sandblasting. Mechanical grinding is suitable for small workpieces, using sandpaper or grinding wheels to remove surface impurities; chemical rust removal uses pickling fluid to react with metal oxides to achieve the purpose of rust removal, but care must be taken to prevent excessive corrosion of the metal substrate by the acid; sandblasting uses high-speed abrasive jets to impact the metal surface, which not only removes impurities but also creates a certain degree of surface roughness, improving the adhesion of the coating. It is widely used in the pretreatment of large steel structures.
Metal air spraying technology continues to develop and improve. The development of new spray guns has effectively increased paint utilization and coating uniformity. For example, high-pressure airless spray guns pressurize the paint using a high-pressure pump, achieving atomization without the need for compressed air, reducing paint waste and environmental pollution. Furthermore, the widespread application of environmentally friendly coatings has made metal air spraying more aligned with the requirements of green development. In the future, as industrial automation levels increase, metal air spraying will be combined with robotics to achieve automated and intelligent coating processes, further improving production efficiency and coating quality, and meeting the increasingly stringent requirements for metal surface treatment across various industries.
