Effective of Surface Active Elements on the Selective Oxidation of Fe-Mn and Fe-Si Alloys

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The legislative requirements for increased vehicle fuel efficiency in order to decrease transportation sector greenhouse gas emissions is driving automotive manufactures to reduce vehicle weight while maintaining vehicle safety and durability. To achieve this goal, manufacturers are employing increasing amounts of advanced high strength steels in their designs such that material specific strength can be increased and material cross-sections reduced. However, the use of reduced cross-sections increases the need for corrosion protection of the steels in order to maintain vehicle integrity, safety and meet consumer durability expectations. Zinc (Zn)-based metallic coatings applied by the continuous galvanizing (CGL) process is the most cost effective means of achieving this goal. However, the newest grades of advanced steels have higher alloy contents, which make the process of reactive wetting and strong coating adherence difficult due to alloy element mainly manganese (Mn) and silicon (Si) selective oxidation in the CGL process. There are several means of overcoming this difficulty, with the use of internal oxidation in which harmful oxides are formed inside the substrate, leaving a good surface and the use of surface active elements, such as small additions of tin (Sn), or combinations of the two, being currently under investigation by the McDermid research group for the next generation of highly alloyed advanced steels. The present proposal seeks to address the fundamental question of the effect of the primary alloying elements in the next generation of advanced steels Mn and Si on the efficacy of surface active alloying additions, in particular Sn, in altering the external oxides morphology such that the substrates are compatible with the CGL process. The findings of this investigation will be leveraged with McDermid's other activities on the design of the next generation of advanced steels such that they are both compatible with the continuous galvanizing process and meet the increasingly demanding property targets of the automotive materials sector. This project will train two PhD level researchers who will have advanced knowledge of surface and property oriented steel designs, and which will help enable Canadian manufacturers to produce lighter, safer, sustainable, fuel efficient vehicles and which will help promote the knowledge-based and sustainable manufacturing sector of the future.