How to Choose the Right Atomizing Air Pressure

The atomizing air pressure largely determines the degree of atomization and flight speed of the sprayed particles and affects the performance of the coating. The same atomizing air pressure has different atomizing effects on different gun designs. A good gun design should concentrate the atomizing airflow at the tip of the molten wire, making the high-speed airflow cut the metal droplets into flakes, separated from the arc area, and further atomize and accelerate the particles. For a particular spray gun, when spraying a wire, high atomization air pressure will result in a highly dense coating with constant other process parameters.

When spraying the self- bonded material to make the bonding, it is often not desirable to use a large atomizing air pressure to obtain a fine coating. On the contrary, the slightly larger spray particles can carry more heat, making micro metallurgical combination with the base metal.

Sometimes some low melting point materials do not want to have too high atomization air pressure, because the melting point of the material is low, the high atomization pressure will make the droplet smaller and accelerate the droplet oxidation and cooling. Before the spray particles reaches the surface of the workpiece, many of the smaller or severely oxidized droplets have solidified and hardened and are bounced off when striking the surface of the workpiece, which reduce the deposition rate of the coating. For example, this phenomenon can be clearly observed when spraying a zinc coating.

Compressed air is the most economical atomization gas source. In the steel structure spraying engineering, a large area of ​​anti-corrosion is required, so compressed air is mainly used as atomizing gas. In order to avoid the excessive oxidation of certain materials, sometimes, the use of nitrogen as the atomization source can obtain very dense coatings with seldom oxide content. Meanwhile the coating mechanical properties are also significantly improved. Due to the large amount of gas consumed during arc spraying, the extensive use of bottled nitrogen can cause economic and operational difficulties, thus limiting its application.