Evaluation of bare spot defects in hot dip galvanizing and their influence on the properties of steel sheet

A. Azimi Dastgerdi,; F. Ashrafizadeh,; M. R. Toroghinejad,; F. Shahriari,; H. Zahraei,

Evaluation of bare spot defects in hot dip galvanizing and their influence on the properties of steel sheet

Authors

A. Azimi Dastgerdi ¹

fakhreddein ashrafizadeh ²

Mohammad Reza Toroghinejad ²

F. Shahriari ³

H. Zahraei

¹ Corresponding Author Address: Steel Institute of Isfahan University of Technology

² Department of Materials Engineering, Isfahan University of Technology

³ Mobarakeh Steel Company

Abstract

In this paper, bare spot defects in hot-dip galvanized sheets were studied in terms of the microstructure and their influence on the corrosion and mechanical properties. Surface characteristics and microstructural features were examined by scanning electron microscopy equipped with energy dispersive spectroscopy microanalysis system. The results showed that the major cause of the bare spots was the lack of wetability of the sheet surface due to contamination, improper heat treatment or chemical composition. Corrosion resistance was evaluated by standard salt spray test. Mechanical properties were examined by tensile testing. The time to red rust was much shorter on the bare spots as compared to other regions, but it appeared that bare spot defects had no significant effect on the mechanical properties of the galvanized steel sheets.

Keywords

hot dip galvanizing

bare spot

surface defects

salt spray test

corrosion resistance