Corrosion Protection of Cu, Fe, Mn and Co Surfaces

The mechanisms and effectiveness of corrosion protection provided by thin ion-beam carbon coatings on Cu, Fe, Mn and Co are discussed. A thin (# 10 A) layer of protective carbon is produced on metal surfaces by ion-beam dissociation of adventitious or intentional hydrocarbon adsorbates. Below 200°C, oxidation is strongly inhibited, as is corrosion in a humid, sulphurous ambient. Above 200°C, the carbon layer may itself be destroyed by oxidation, due to catalytic action of the metal surface. Thicker PVD carbon (up to 60 A) was not an effective corrosion barrier, even after ion irradiation. A technique for producing high integrity ion-beam carbon layers of high stability and durability is discussed.