Corrosion behaviour of electrodeposited and sputtered Cr coatings and sputtered Ta coatings with α and β phases

The corrosion behaviour of α- and β-Ta coatings was compared to that of Cr coatings produced by cylindrical magnetron sputtering as well as electrodeposition. For Ta coatings, the corrosion process was dominated by dissolution of the steel substrate through open pores, however, at the end of 5 days, coating degradation was not observed. In contrast, while open pores were not observed with the Cr coatings, the corrosion resistance decreased as a function of time under acidic conditions, as a result of the protective oxide dissolution. Initially, however, the sputtered Cr coating exhibited improved corrosion resistance over the electrodeposited one, potentially due to the surface structure of the oxide film. Both Cr coatings showed similar transpassive behaviour to that of pure Cr; the current density of the sputtered Cr coating was observed to be greater than that of the electrodeposited one in the transpassive region due to the extensive droplet-like defects.

[1]  M. Pourbaix.  Atlas of Electrochemical Equilibria in Aqueous Solutions , 1974 .

[2]  G. Chapuis,et al.  The self-hosting structure of β-Ta , 2002 .

[3]  N. Hara,et al.  Corrosion characteristics of Fe2O3Cr2O3 artificial passivation films under potentiostatic control , 1995 .

[4]  B. E. Wilde,et al.  The cathodic discharge of hydrogen on active and passive chromium surfaces in dilute sulphuric acid solutions , 1969 .

[5]  J. Ross Macdonald,et al.  Impedance spectroscopy , 2006, Annals of Biomedical Engineering.

[6]  H. Groult,et al.  Dielectric properties of anodic oxide films on tantalum , 1995 .

[7]  C. Rickard,et al.  Analysis of magnetron-sputtered tantalum coatings versus electrochemically deposited tantalum from molten salt , 1999 .

[8]  W. Ho,et al.  Effect of substrate surface roughness on the characteristics of CrN hard film , 1996 .

[9]  Dean W. Matson,et al.  Properties of thick sputtered Ta used for protective gun tube coatings , 2001 .

[10]  L. Fedrizzi,et al.  Wear-corrosion mechanism of hard chromium coatings , 2002 .

[11]  M. H. Read,et al.  X-ray analysis of sputtered films of beta-tantalum and body-centered cubic tantalum , 1972 .

[12]  Shenhao Chen,et al.  Electrochemical behaviour of chromium in acid solutions with H2S , 1999 .

[13]  D. Matson,et al.  High-rate sputter deposited tantalum coating on steel for wear and erosion mitigation , 2002 .

[14]  Investigation of the structure of β-tantalum , 2002, cond-mat/0208122.

[15]  A. Matthews,et al.  An electrochemical impedance spectroscopy study of the corrosion behaviour of PVD coated steels in 0.5 N NaCl aqueous solution: Part II.: EIS interpretation of corrosion behaviour , 2003 .

[16]  M. Sosnowski,et al.  Tantalum films for protective coatings of steel , 2004 .

[17]  D. Gabe,et al.  Porosity of Electrodeposited Coatings: Its Cause, Nature, Effect and Management , 1992 .

[18]  J. G. Kim,et al.  Localized corrosion mechanisms of the multilayered coatings related to growth defects , 2004 .

[19]  G. Sundholm,et al.  Conduction mechanism of the anodic film on chromium in acidic sulphate solutions , 1998 .

[20]  F. Mansfeld,et al.  Determination of the long term corrosion behavior of coated steel with A.C. impedance measurements , 1983 .

[21]  The structure and stability of β-Ta thin films , 2004, cond-mat/0407178.

[22]  Paul L. Cote,et al.  Laser pulse heating of gun bore coatings , 2001 .