Evaluation of superficial chemical treatmentto improve the performance of thermal sprayed aluminium coatings

Abstract

The objective of this research is to study the behaviour of thermal sprayed aluminium coatings after the application of superficial chemical treatments; for this purpose, 11 types of chemical solutions were applied on carbon steel probes (10 cm í— 15 cm í— 3 mm) which were previously thermal sprayed with aluminium coatings; and evaluated according to ISO 11474 in accelerated environment for 5 months. The test probes were evaluated monthly by visual inspection and photographic record, and withdrawn at 2, 4 and 5 months of exposure for their further analysis in laboratory. Corrosion rate and the behaviour of thermal sprayed coatings were evaluated using electrochemical techniques: Electrochemical Impedance Spectroscopy (EIS) and Anodic Potentiodynamic Polarization Curves (ASV). The treatments of sulphuric acid, oxalic and aloe vera increase the performance of thermal spayed aluminium coating; while commercial rust converter and tannin decrease its performance.

Keywords

• thermal sprayed coating
• superficial chemical treatment
• electrochemical techniques