A Comparative Research on Corrosion Behavior of Electroplated and Magnetron Sputtered Chromium Coatings

Chromium deposits rank among the most widespread metal coatings for functional and decorative purposes. However, electrodeposition from Cr(VI) aqueous solution, which is the industrial process currently used to achieve thin chromium deposits, presents several environmental issues, urging the development of alternative solutions. In this study, which aims to compare the functional and aesthetical properties of decorative coatings, 800 nm thick chromium layers were deposited directly onto copper substrates by means of magnetron sputtering (MS) and direct current electrodeposition (ED). The obtained coatings were characterized regarding their thickness, morphology, color index, chemical composition, and corrosion resistance viewpoints. With respect to the electroplated samples, which constitute the benchmark, the magnetron sputtered ones appeared to be darker but showed a pleasing reflective appearance and superior thickness homogeneity, as well as the absence of voids and macrocracks, as evidenced by scanning electron microscopy (SEM) investigation. Regarding the anticorrosion performances of the chromium layers, electrochemical and standard salt spray test (NSS test) were carried out at room temperature in 3.5% NaCl solution, and evidenced similar, if not better, results for the magnetron sputtered coatings. On the whole, the data displayed here demonstrates the suitability of magnetron sputtering technology for use as an industrially feasible finishing technology for both aesthetic and mild-condition anticorrosion purposes.