Coating technologies are widely used in manufacturing processes, to prevent products from deterioration due to the actions of water, air, or an acid, to improve the artistic functions of product. In advance of nano-technologies, the geometry of coating particles will be fabricated as designed. Therefore, the effects of the geometry of materials on the coating quality should be considered in manufacturing processes. Surface roughness is one of the major indicators of coating quality. The correlation of geometry of coating materials and surface roughness on the performance of coated electrodes is presented in this paper. Three types of geometries are analyzed which are spherical particles, uniformly distributed columns, and random types. Besides the geometry of coating materials, the impact force resulting from spray jet will alter the surface roughness and is one of the important factors to coating quality. Therefore, the stability of coating jet is also studied. The findings show that high frequency waves can be added into the flow to get neutrally stable condition which will improve the stability of impact force.