Electrochemical behaviour of molybdenum based coatings obtained by organometallic chemical vapour deposition

Abstract

Coatings were prepared by chemical vapour deposition from bis-(tricarbonyl cyclopentadienyl molybdenum). Homogeneous and compact coatings were obtained at a deposition temperature of 400°C for 4 h or 375°C for 7 h. Various analytical techniques were used to determine the compositions of the coatings. The electrochemical behaviour in0 various corrosive media of coatings deposited on various metallic substrates was studied by a polarisation technique. In neutral chloride solution the coating increases the resistance of copper and magnesium to general dissolution and the resistance of 18Cr–10Ni stainless steel to pitting corrosion. In hydrochloric acid solution the coating reduces the dissolution rate of copper; in sulphuric acid solution the corrosion potential becomes more positive and the corrosion rate decreases when copper and stainless steel are coated. However, the coatings undergo progressive dissolution in these media when the applied potential is > 100 mV more positive than the corrosion potential.