Electrochemical corrosion behaviour of Mg–Al alloys with thermal spray Al/SiCp composite coatings

Abstract

The corrosion protection of Mg–Al alloys by flame thermal spraying of Al/SiC particles (SiCp) composite coatings was evaluated by electrochemical impedance spectroscopy in 3.5 wt.% NaCl solution. The volume fraction of SiCp varied between 5 and 30%. The as-sprayed Al/SiCp composite coatings revealed a high number of microchannels, largely in the vicinity of the SiCp, that facilitated the penetration of the electrolyte and the subsequent galvanic corrosion of the magnesium substrates. The application of a cold-pressing post-treatment reduced the degree of porosity of the coatings and improved the bonding at the coating/substrate and Al/SiC interfaces. This resulted in improved corrosion resistance of the coated specimens. The effectiveness of the coatings slightly decreased with the addition of 5–30 vol.% SiCp compared with the unreinforced thermal spray aluminium coatings.

Keywords:

• magnesium alloys
• composite coatings
• corrosion
• thermal spraying

Acknowledgements

The authors would like to express their gratitude to MYCT for financing this work (Project MAT2006-13179-C02-02).

Notes

1. Email: [email protected]

Additional information

Notes on contributors

S. Feliu

1