Inhibition Breakdown Kinetics of Dual Phase Steels

The desire to improve automotive fuel efficiency through vehicle light weighting has resulted in the increased use of advanced high strength steels (AHSS) such as dual phase (DP) steels in automotive structures. In order to meet consumer safety and durability demands, robust corrosion protection is essential as material cross-sections are reduced. The continuous galvanizing line (CGL) process is the most cost effective method of providing corrosion protection to ferrous alloys and is heavily used throughout the steel industry. However, the use of alloying elements such as Mn, Cr, and Si in AHHS chemistries can result in selective oxidation during annealing, leading to problems with reactive wetting and galvannealing kinetics. The objective of this research is to determine the inhibition breakdown kinetics of DP steels as a function of time and alloy Mn content. To accomplish this, selective oxidation and inhibition breakdown studies were performed on four substrates with Mn contents ranging from 0-2.5 wt. % Mn.