Microstructural changes and their influence on corrosion post-annealing treatment of copper and AISI 5140 steel in 3.5 wt% NaCl medium

Abstract

Corrosion is one of the major issues faced by marine industries. Two of the major metals used in these industries include copper and AISI 5140 steel. This iterates the importance of understanding the microstructure and its influence on the corrosion behavior of these metals in 3.5 wt% NaCl that is studied here. Annealing treatment was performed for both the metals, and the microstructure before and after the annealing treatment was performed using an optical microscope and SEM. X-ray diffraction (XRD) of the metals before and after heat treatment was performed, and it was found that the annealing treatment caused an increase in the crystallite size irrespective of the metal. The samples were subjected to Vicker’s microhardness testing, and a decrease in the hardness was achieved post-annealing. The electrochemical studies further proved that there is an improvement in corrosion resistance post-annealing. The kinetic and thermodynamic parameters are described using Arrhenius and transition state theories.

Keywords:

• corrosion
• annealing
• 3.5 wt% NaCl
• AISI 5140 steel
• copper
• EIS
• PDP

Acknowledgments

The authors extend their acknowledgment to the Department of Chemistry, Department of Mechanical & Manufacturing Engineering, Central Instrumentation Facility, Manipal Institute of Technology (MIT), Manipal, and Manipal Academy of Higher Education (MAHE) for the characterization facilities. The first author extends her appreciation to MAHE, Manipal for providing the Dr. TMA Pai scholarship.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Inquiries about data availability should be directed to the corresponding author.

Additional information

Funding

This work was supported by intramural funding from the Manipal Academy of Higher Education, Manipal