The hazardous hexavalent chromium formed on trivalent chromium conversion coating: The origin, influence factors and control measures

► We use different treating-agents to compare and evaluate the presence of hexavalent chromium on trivalent chromium conversion coating. ► The processing parameters have significant effect on the presence of hexavalent chromium. ► The production of hexavalent chromium is likely dependent on the complexing agent. ► The addition of sodium nitrate and cobalt sulfate increase the amount of hexavalent chromium. ► The hydroxyl compound d-gluconic acid can inhibit the amount of hexavalent chromium to an extent.