In this galvanic process, a zinc coating is deposited onto the product surface by means of electrolysis. The electrolytic process uses an aqueous zinc solution. The result is a smooth and bright layer. The layer thickness varies from 5 – 40 µm and this is determined by the current density and the immersion time in the zinc bath. The galvanised layer is then treated with passivation solutions such as chrome or bichromate, which increase the corrosion resistance and give a decorative appearance. The passivation layer is a thin zinc-chromium/zinc-oxide layer on top of the zinc coating. The zinc coating has a translucent yellow hue, which is (at least) slightly thicker than that of coatings applied using “traditional” electrolytic galvanising. This process comprises oxy-hydrogen gas, which, in the case of forged steel types, can be absorbed into the material structure. There is no risk of material deformation.
The presence of oxy-hydrogen gas may have adverse effects such as hydrogen embrittlement. Consequently, fractures or tears may occur. The higher the tensile strength class, the greater the risk is of this occurring. Certainly, with steel grades higher than 8.8, the hydrogen absorbed into the steel can result in significant loss in ductility, the so-called hydrogen embrittlement. The likelihood of hydrogen embrittlement cannot be ruled out. Stokvis Trading BV does not accept any liability whatsoever in this respect.
Starting 2019, the use of Chrome VI will have to be minimized as a result of the European Health and Safety and Environment Policy (REACH regulations). This substance can be found in the mixture of this surface treatment. Ask our employees about possible alternatives or the recent possibilities.