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Enhanced corrosion resistance of magnesium and its alloys through the formation of cerium (and aluminium) oxide surface films
Author(s) -
Ardelean H.,
Marcus P.,
Fiaud C.
Publication year - 2001
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/1521-4176(200112)52:12<889::aid-maco889>3.0.co;2-0
Subject(s) - cerium , magnesium , corrosion , x ray photoelectron spectroscopy , aluminium , oxide , materials science , electrochemistry , inorganic chemistry , cerium oxide , metallurgy , chemistry , chemical engineering , electrode , engineering
Cerium (and aluminium) oxide layers were formed on magnesium and its alloys (AZ91) by chemical surface treatment with or without subsequent annealing. The corrosion behaviour modifications provided by the formation of these surface films were studied by means of different electrochemical and surface analysis techniques. The electrochemical behaviour, studied in sodium sulphate (Na 2 SO 4 ) solution, showed (i) a marked shift of the corrosion potential towards more positive values, (ii) a slight inhibition of the cathodic reaction and (iii) a significant decrease of the anodic dissolution current. X‐ray photoelectron spectroscopy (XPS) was used for the characterisation of the composition of the deposited films and of the changes in the film composition during the electrochemical corrosion tests. The components of some oxide films are cerium dioxide (CeO 2 ), aluminium oxide (Al 2 O 3 ) and aluminium hydroxide (Al(OH) 3 ). Other metallic mixed oxide films were obtained as a function of the solution composition. Very little (or no) change in the oxide film composition during the cathodic and anodic polarization experiments was observed from XPS measurements. Chemical treatment provides thick and moderately adherent protective oxide films. Annealing under oxygen further improves the beneficial effect of the chemical treatment.