Resistance of different Zn coatings at elevated temperature air environments

Abstract

In this work, the structure and oxidation behaviour of three different zinc coatings were examined. The coatings were formed with hot dip galvanizing, pack cementation and thermal spray methods. Three different oxidation conditions were selected for the tests, which correspond to low, medium and intensive oxidation conditions. The oxidized samples were examined by scanning electron microscopy and X-ray diffraction. Results showed that the thermal spray coatings are far more susceptible than the others and suffer from extreme oxidation because of the porous net existing in the coating, which provides diffusion paths to oxygen. Hot dip and pack coatings were proved more resistant under the same exposure conditions, mainly due to the presence of different Fe–Zn phases in their structure and their morphological homogeneity.

Keywords:

• Coatings
• Zinc
• Galvanizing
• Pack cementation
• Thermal spray
• Air oxidation