Experimental Relationships between Surface Roughness, Glossiness and Color of Chromatic Colored Metals

Abstract

This paper describes the establishment of an evaluation method for metal surface texture. The evaluation parameters used for surface texture were roughness, glossiness and color. Seven sample materials were studied: aluminum alloys (A2017, A5052), stainless steel (SUS304) and copper alloys (tough pitch copper C1100, brass C2801, phosphor bronze C5191 and nickel silver C7541). The surfaces of all specimens were polished using waterproof abrasive papers. The correlation of the surface texture parameters for all specimens was investigated experimentally. The surface roughness of specimens was evaluated using the arithmetical mean roughness “Ra”. The method for evaluating surface color was assessed by using CIELAB color space. The CIELAB color space is one of a uniform color space defined by CIE (Commission Internationale de l'Eclairage) in 1976. The results indicated that as surface roughness value “Ra” decreased, as the glossiness value “Gs(60°)” increased exponentially. The lightness value “L^*” of the CIELAB color space decreased, as surface roughness value “Ra” decreased. Thus, the relationship between the lightness value “L^*” and surface roughness value “Ra” showed an inverse correlation with the glossiness value “Gs(60°)” and surface roughness value “Ra”. Moreover, the surface color showed that the blue hue increased, as the surface roughness value “Ra” decreased for all seven types of materials.