Corrosion Resistance Studies of Austenitic Stainless Steel Grades in Molten Zinc-Aluminum Alloy Galvanizing Bath
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TECHNICAL ARTICLE—PEER-REVIEWED
Corrosion Resistance Studies of Austenitic Stainless Steel Grades in Molten Zinc-Aluminum Alloy Galvanizing Bath ¨ zcan Roland Tolulope Loto . Emre O
Submitted: 23 March 2016 / Published online: 26 April 2016 Ó ASM International 2016
Abstract The corrosion inhibition performance and mechanical behavior of galvanized and heat-treated four newly developed austenitic stainless steel grades and type 316L austenitic stainless steel for application as sink rolls in galvanizing baths of 0.14–0.21 wt.% aluminum was investigated and compared through immersion corrosion test to determine the weight loss between 168 and 504 h, tensile test, and Charpy impact test. The delta ferrite content of the test samples was observed and estimated through optical microscopy, feritscope, and ONRL diagram. Scanning electron microscopy and energy dispersive spectroscopy were used to characterize the surface microstructure, morphology, and chemical composition of the galvanized coating of the steel samples. Result showed that only two of the newly developed stainless steel compositions were selected for use in fabrication of galvanizing hardware based on the comparisons of corrosion and mechanical performances of tested alloys. Keywords Austenitic stainless steel Corrosion Microstructure Mechanical test
R. T. Loto (&) Department of Mechanical Engineering, Covenant University, Ota, Ogun, Nigeria e-mail: [email protected] R. T. Loto Department of Chemical, Metallurgical & Materials Engineering, Tshwane University of Technology, Pretoria, South Africa ¨ zcan E. O Metallurgical and Materials Engineering Department, Middle East Technical University, Ankara, Turkey
Introduction Corrosion prevention and control through application of a protective zinc coating to stainless steels is one of the most reliable, cost-effective, long-lasting, and environmentally friendly methods in current application [1, 2]. Automotive body parts and components, office cabinets and drawers, doors, gates and body parts of air conditioners, refrigerators, dishwashers, roof tops, etc., are some of the major areas of application for galvanized steel sheets; however, increase in demand of galvanized sheet has resulted in problems in quality and efficiency of production. High-grade galvanized steel in sufficient quantity is required to match the increasing industrial demand internationally. Stainless steels fabrications for zinc bath hardware of continuous galvanizing lines corrode significantly due to various factors in molten zinc and aluminum media. At present, there are over 450 continuous galvanizing lines where the coating of steel sheet with liquid zinc-aluminum alloy is performed worldwide (Fig. 1) [3]. Studies on the development of more resistant and cost-efficient materials have been scarce until the last decade. The challenge to develop superior materials in continuous galvanizing lines is ever increasing [4]. The corrosion resistance of sink rolls is vital industrially due to the effect of corrosion damage on the surface
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