The conversion of the waste Cr(VI) electroplating bath to Cr(III) electroplating bath

The scope of this study is to protect the environment from the waste of Cr(VI) electroplating bath and convert it to the useful product. As known, Cr(VI) is a toxic materials and harmful for the health of workers and environment. Therefore, this study has aimed to develop the conversion process of the waste Cr(VI) electroplating bath to Cr(III). To identify the significant factors affecting the quality of Cr coating during the conversion, experimental design methodologies were applied. A full factorial experimental design was performed to specify the effects and interactions of the main factors and optimize the conversion process. The results were analysed statistically. The surface response method was carried out to determine the stability of the Cr(III) bath after the conversion. The maximum brightness was observed when the amount of sodium sulphate was 80-90 g/L and boric acid 60-65 g/L at pH 3.25. Coating defects were investigated using a scanning electron microscope (SEM). EDS measurements were taken to analyse the composition of the Cr coating. SEM images and EDS measurements indicated that the blackness and matte defects are due to the formation of sulphur in the Cr coating.