Electropolishing effect on roughness metrics of ground stainless steel: a length scale study

Abstract

Electropolishing is a widely-used electrochemical surface finishing process for metals. The electropolishing of stainless steel has vast commercial application, such as improving corrosion resistance, improving cleanness, and brightening. The surface topography characterization is performed using several techniques with different lateral resolutions and length scales, from atomic force microscopy in the nano-scale (<0.1 µm) to stylus and optical profilometry in the micro-and mesoscales (0.1 µm-1 mm). This paper presents an experimental length scale study of the surface texture of ground stainless steel followed by an electropolishing process in the micro and meso lateral scales. Both stylus and optical profilometers are used, and multiple cut-off lengths of the standard Gaussian filter are adopted. While the commonly used roughness amplitude parameters (Ra, Rq and Rz) fail to characterize electropolished textures, the root mean square slope (RΔq) is found to better describe the electropolished surfaces and to be insensitive to scale.

Corrosion Properties of Electropolished AISI 316L Austenitic Biomaterial in Relation to Electropolishing Conditions

“…The roughness of all tested surfaces was evaluated by Ra (roughness average), Rz (average maximum peak to valley height) and R∆q (root mean square slope) parameters (measurements performed by Mitutoyo SJ 400). According to the authors [9] R∆q parameter is better for the description of the electropolished surfaces than commonly used roughness amplitude parameters and unlike to them it is insensitive to the scale. The above mentioned roughness parameters of all tested surfaces are listed in Table 3.…”

“…Electrolytic baths for electropolishing are mostly concentrated acid solutions, such as mixtures of sulphuric acid and phosphoric acid or mixtures of perchlorates with acetic anhydride and methanolic solutions of sulphuric acid [13,14]. For the electropolishing of stainless steels biomaterials mixtures of orthophosphoric acid, sulphuric acid and water/glycerine (for the viscosity increasing) of various ratios of used acids [3,4,8,9] are recommended. Recommended temperatures range is commonly from 40 to 90 ºC [3,4,9,18].…”

“…For the electropolishing of stainless steels biomaterials mixtures of orthophosphoric acid, sulphuric acid and water/glycerine (for the viscosity increasing) of various ratios of used acids [3,4,8,9] are recommended. Recommended temperatures range is commonly from 40 to 90 ºC [3,4,9,18].…”

Plasma Electrolytic Polishing—An Ecological Way for Increased Corrosion Resistance in Austenitic Stainless Steels

“…(a) Marked differences between the as received and both polished surfaces were reflected in the surface roughness evaluated by the following roughness parameters (Table 4): arithmetical mean deviation of the assessed profile (Ra), the average maximum peak to valley height (Rz), and the root mean square slope (R∆q). The R∆q parameter is recommended for the description of the real roughness of the electropolished surfaces because its insensitivity to the scale is unlike the commonly used roughness amplitude parameters [24]. According to the presented results, the roughness of both plasma-polished surfaces is very similar.…”

Electropolishing and Shaping of Micro-Scale Metallic Features

“…The origin of electropolishing was marked by the use of sulfuric and phosphoric acid solutions (acid content: 50–80%, surfactants: water/glycerol 30–10%) to reduce the surface roughness (Sa and Rz) of metals and alloys like copper, nickel, steel, titanium, niobium, magnesium, and aluminum [ 2 , 14 , 20 , 21 , 22 , 116 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 ]. The reason for their widespread use is that sulfuric acid provides a sufficiently large bath conductivity, and phosphoric acid is primarily responsible for the polishing of the metal surface [ 148 ].…”