Effect of AlCl 3,CH 3 SO 3 H on thickness,current efficiency and corrosion properties of brush plated Cr(III) formate urea baths

Abstract

Brush plating technique was used to deposit trivalent Cr for the first time and effects of AlCl₃ and methane sulphonic acid (CH₃SO₃H) in the trivalent Cr bath was studied. Advantages of brush plated Cr on suitable substrate produced by selective area deposition process with required thickness was investigated. Owing to its portability, flexibility and easy to operate, brush plating has found increasing use in industry. The main applications are for repair and resizing purposes. Brush plated Cr on brass substrate has been investigated using XRD, SEM and AFM. X-ray diffraction analysis revealed that the brush plated Cr(110) was crystalline. Uniform surface coverage of the substrate by granular morphology was observed from SEM and AFM. CH₃SO₃H increases the hydrogen overpotential on Cr deposition, therefore current efficiency and thickness increased. Cr coated from bath containing both AlCl₃ and CH₃SO₃H have better corrosion resistance due to high charge transfer resistance R _ct and very low I _corr than Cr(III) bath without these additives.