SURFACE STUDY OF THE EFFECT OF PB2+ AND CA2+ ON THE ADSORPTION OF PHOSPHONIC ACID ON POLYCRYSTALLINE IRON

The adsorption of a corrosion inhibitor (1-hydroxy-ethane-1,1-diphosph onic acid, HEDP) from neutral aqueous solutions on the surface of mild steel samples was studied by the help of surface analytical methods ( XPS, XAES). The experiments revealed that Pb and Ca impurities (origin ating from pro analysi grade chemicals used for sample preparation) we re enriched on the sample surface during the adsorption of HEDP. It wa s also observed that the P 2p and P KLL signal intensities were strong ly influenced by the presence of these impurities. A systematic invest igation of the effect of the Pb2+ and Ca2+ cations on the inhibitor ad sorption has also been carried out.