Electropolishing (EP) is a non-conventional polishing method that follows anodic dissolution. The polishing setup comprises of an anode (sample to be electropolished), a cathode (tool), and an electrolyte. In EP, the electrolyte in mainly consists of viscous acidic fluid. During EP, the hydrogen gas is evolved at the tool and oxygen gas at the workpiece followed by anodic dissolution, as shown in Fig. 1. Due to the diffusive mechanism in EP, as explained by Jacquet's viscous film theory , a viscous film forms over the workpiece surface. This viscous layer increases electrical resistance for anodic dissolution. A thick layer forms on the valley, whereas a thin layer forms on the anode's protruding surface. Due to this difference in the layer thickness, a higher resistance for anodic dissolution for valleys than protruding surfaces is observed. This creates a polishing effect by removing the protruding surface first, followed by the valley. Hence, the surface is leveled and polished during EP . It does not change the actual property of the bulk metal and also forms a stable passive oxide layer which increases the corrosion resistance .
During electropolishing, oxygen gas evolves at anode forming bubbles and moves away the electropolishing solution from the anode film surface. Hence, the protruding surface on the workpiece dissolves faster, while the valley remains inaccessible . EP does not change the crystallographic and grain-boundary structure of the bulk material and never induces any residual stress, which makes it different from other polishing methods . This advantage of EP is utilized as a post-processing method for components fabricated by thermal-induced processes like laser beam machining (LBM), Electric discharge machining (EDM), etc.
This paper performs EP of maraging steels as it offers competitive alternative materials for aerospace structures while exhibiting ultra-high-strength and good corrosion resistance . It is widely used as raw powders in additive manufacturing to fabricate complex parts .
Oliveira et al.  used the powder bed fusion process for 3D printing of maraging steel 300. The effects of cutting parameters like feed per tooth and cutting speeds on the surface conditions, namely average roughness and residual stress during milling, were investigated. Surface roughness of 3.30 µm was obtained after additive manufacturing. Milling was used as a post-processing technique to reduce the surface roughness to 0.31 µm at 250 m/min cutting speeds and 0.02 mm/tooth feed per tooth. Compared to EP, the conventional milling process directly contacts the workpiece, changes workpiece’s grain structure completely, and induces compressive residual stress.
Li et al.  polished maraging steel by micro-grinding and achieved a minimum roughness of 0.67 µm. They found that while polishing at a very high speed, the metal surface property changes drastically. They proposed a small grinding wheel with a very low rotating speed to avoid this. Also, residual stress was induced on the workpiece surface while polishing by micro-grinding . These disadvantages of conventional polishing methods make way for researchers to proceed in non-conventional polishing methods.
Very few literatures are found for the electropolishing of maraging steel. As it is a Ni-based alloy, the author tries to find the electrolyte for the electropolishing of Ni-based alloys. Huang et al.  had utilized perchloric-acetic mixed acids electrolyte to investigate the EP behavior of Inconel 718 alloy. Anodic polarization curves at different concentrations of perchloric acid (HClO4) were analyzed, and it was concluded that more than 50 vol.% of HClO4 provides better anodic dissolution. EP enhances the corrosion resistance of Inconel 718 alloy. For Ni-based alloys, perchloric-acetic acid mixtures are generally used as an electrolyte –. Aksu et al.  had electropolished Fe-Ni-Co alloy in perchloric acid solution with acetic acid as a solvent. Linear sweep voltammetry was performed to find the current density for different concentrations of perchloric acid. An investigation was conducted to analyze the effect of electrolyte concentration, current density, and bath temperature on surface roughness and thickness change. Surface roughness of 0.05 µm is achieved.
Wang et al.  had investigated the parameters of electropolishing on the surface quality of Ni-Ti shape memory alloy after milling. It was observed that better the initial surface homogeneity, better would be EP effect. Methanol-perchloric acid mixture was used as an electrolyte to achieve a minimum roughness of 0.279 µm. Han and Fang  had compared NaCl-based electrolyte with H2SO4-based electrolyte for EP of stainless steel 316L. It was observed that the NaCl-based electrolyte has a higher current density, which leads to a higher material removal rate. Surface roughness of 20.4 nm and 100 nm had been achieved for the respective electrolytes.
In the present study, electropolishing of maraging steel is performed. An organic electrolyte solution containing acetic acid with perchloric acid is used for electropolishing. The various parameters like polishing time, temperature, and agitation are analyzed. Linear sweep voltammetry (LSV) is performed to generate the polarization curve for maraging steel at a particular solution. Energy-Dispersive X-Ray Spectroscopy (EDS) analysis is performed to investigate the workpiece surface composition before and after EP. The influence of EP parameters on surface roughness as well as surface reflectance is also presented. The contact angle of the surface is measured with the help of a goniometer to analyze the workpiece surface's wettability before and after EP. Corrosion behavior of the sample before and after EP is also studied.