Most metal AM technologies are rapidly approaching, and in some cases even exceeding the Technology Readiness Level 8, indicating that they are widely available and capable of completing a wide range of projects despite identified process restrictions. Thanks to significant technological progress made in the last decade, more industries are incorporating metal additive manufacturing in their production process to obtain highly customized parts with complex geometries. However, the poor surface finish of AM parts is a major drawback to their aesthetics and functionality. Over the years, different approaches were proposed to enhance their surface quality, each bearing its limitations. Among the proposed technologies, electropolishing is a strong candidate for improving the surface finish of AM parts. This study aims to review the literature on electropolishing of AM parts. However, to provide a comprehensive study of the different aspects involved, a brief review is also presented on the origin and consequences of the surface properties of AM parts as well as an evaluation of other available post-treatment technologies. Finally, the existing challenges on the way and potential countermeasures to expedite the industrial application of the electropolishing process for post-treatment of AM parts as well as future research avenues are discussed.

MoS₂-based solid lubricants have obtained significant attention and are extensively employed in the aerospace industry due to their desirable tribological performance. However, to enhance their performance in humid environments, MoS₂ is often doped with Pb-based compounds. Considering the health and environmental concerns associated with Pb, it is necessary to develop eco-friendly alternatives. In this study, hexagonal boron nitride (hBN) has been used as a potential substitute for Pb-based dopants in MoS₂-based solid lubricants and coatings with varying hBN contents (9.5, 11.5, 13.5, 15.5, and 17.5 wt.%) were applied to stainless steel substrates using a spray bonding technique. The friction and wear characteristics of the coatings were analyzed by using a ball-on-flat tribometer, employing constant load conditions. Subsequently, ex-situ analysis techniques such as scanning electron microscopy (SEM), raman spectroscopy, and atomic force microscopy (AFM) were used to characterize the coatings. The results showed that the coating with a lower hBN concentration presented improved tribological properties, which was correlated with the development of an effective MoS₂-based transfer/tribo-film. This suggests that optimizing hBN content is crucial for enhancing the lubrication performance.

The effectiveness factor, E _f, (fraction of the electrode surface that participates effectively in the investigated reaction) of fast (Fe³⁺/Fe²⁺), moderate (Cl₂/Cl⁻) and slow (O₂/H₂O) redox couples has been estimated using IrO₂-based electrodes with different loading. The method of choice was linear sweep voltammetry (measurement of the anodic peak current) for the Fe³⁺/Fe²⁺ redox couple and steady-state polarization (determination of the exchange current) for the O₂ and Cl₂ evolution reactions. The results have shown that the effectiveness factor depends strongly on the kinetics of the investigated redox reaction. For the Fe³⁺/Fe²⁺ redox couple, effectiveness factors close to zero (max 4%) have been obtained contrary to the O₂ evolution reaction where effectiveness factors close to 100% can be achieved, all being independent of IrO₂ loading. For the Cl₂ evolution reaction, intermediate values of the effectiveness factor have been found and they decrease strongly, from 100% down to about 60%, with increasing loading.