Properties of ‘Sulpho-Chromispel-I’ electrolyte of standard concentration for the electrodeposition of chromium

SUMMARY

The most important properties of non-standard highly efficient “Sulpho-Chromispel- I” type electrolytes for chromium plating have been investigated. They contain as side anions catalysing the cathodic process, both SO^2-₄ and I⁻. The effects of cathodic current density and concentration of hydroiodic acid on the total current distribution are evaluated. The deposition rate is determined. The effect of operating parameters on the throwing power is established. The properties of the electrolytes studied are compared with those of standard sulphate electrolytes and “Chromispel-I” compositions. The most efficient electrolyte comprises CrO₃:I- = 20:1 and 20 cm³ dm⁻³ sulphuric acid. The deposition rate can reach a value of 250 μm h⁻¹ at a current density of 200 A dm⁻². The throwing power of this electrolyte is close to that of standard sulphate electrolytes. As a whole “Sulpho-Chromispel-I” electrolytes exhibit lower throwing power compared to standard sulphate electrolytes or pure “Chromispel-I” electrolytes. They are recommended for chromium plating details of simple profile.

Keywords:

• chromium plating
• “Sulpho-Chromispel-I” electrolyte
• cathodic processes
• kinetics
• throwing power
• deposition rate