Steel is a cheap renewable material with many interesting properties but its presence in the electroplating sector is very limited due to adhesion difficulties. Stainless steel contains approximately 10.5% chromium, which forms a surface oxide layer that passivates the steel, making it resistant to corrosion [1]. It is the presence of this surface oxide film that makes it difficult to electroplate steel. The aim of electroplating steel is to refine it by depositing nobler metals of the desired color, such as ruthenium and gold.

The activation of steel involves the remotion of the oxide layer. The main method of electroplating stainless steel is generally through the deposition of nickel, but the intensive use of nickel baths makes these processes inappropriate for the sustainability paths taken by the electroplating industry. Even when nickel-based galvanizing processes are not used, it is possible that steel objects do not pass the nickel release test. This is because the steel itself contains nickel, so the removal of the surface oxide layer during the electroplating process may facilitate the release of nickel.

The nickel release mechanism is not yet fully clear but bring to allergenic issues in the final product [2]. We performed a systematic study electroplating various metals and alloys on steel to evaluate which one performed better as barrier against the release of nickel and shed light on this issue.

The steel substrate was characterized microscopically and spectroscopically before and after the release test. The amount of nickel was evaluated in the solution that simulates human sweat to evaluate its release in µm·cm^-2·week^-1 according to the standard EN 1811:2015.

The authors acknowledge Regione Toscana POR CreO FESR 2014-2020 – azione 1.1.5 sub-azione a1 – Bando 1 “Progetti Strategici di ricerca e sviluppo” which made possible the projects “A.C.A.L. 4.0” (CUP 3553.04032020.158000165_1385), “A.M.P.E.R.E.” (CUP 3553.04032020.158000223_1538), “GIGA 4.0” (CUP 3553.04032020.158000105_1242) and “GoodGalv” (3647.04032020.157000060).

References

[1] Olsson, C. O. A.; Landolt, D. Passive films on stainless steels—chemistry, structure and growth. Electrochim. Acta. 2003, 48, 1093-1104, doi:10.1016/S0013-4686(02)00841-1.

[2] Yuan, J.P.; Li, W.; Wang, C.; Ma, C.Y.; Chen, L.X.; Chen, D.D. Nickel release rate of several nickel-containing stainless steels for jewelries. J. Iron Steel Res. Int. 2015, 22, 72-77, doi: 10.1016/S1006-706X(15)60012-7.