TWI Industrial Member Report Summary 449/1992
By M Amin and N O'Rourke
Air atomisation is commonly used in arc spray process because it can be made available anywhere most easily and economically. However, the oxide content of the coatings is excessive which can be detrimental because it reduces the bond strength, so that the coatings flake off prematurely in service. In addition, the porosity level is high which is detrimental because it allows the corrosive liquids and gases to permeate to the substrate. Another disadvantage is that an excessive burnoff of the alloying elements occurs, which are the essential ingredients contained in the parent wires, so that the coatings cannot be produced with a specified composition reliably.
The oxide content, porosity level and burnoff of the alloying elements can be minimised hy nitrogen or argon gas atomisation. In this report. the effects of the atomising gases on the coating characteristics, found by various investigators, have been reviewed.