Effect of Ai–Si coating weights on corrosion of ultra-high-strength steel Usibor^R 1500 used in automotive structures

Abstract

Corrosion is a major factor that inhibits the longevity of automotive components especially in countries where significant amount of salt is sprayed on highways during winter. In this paper the effect of cosmetic, perforation and red pitting corrosion on indirect hot-stamped Ultra-High-Strength-Steel UsiborR 1500 were investigated using two different Al-Si coating weights AS80 and AS150. The experiments were conducted in a cyclic corrosion chamber over 12 weeks. The results show that AS150 and AS80 exhibited similar excellent perforation corrosion resistance compared to 22MnB5 due to highly protective corrosion products; Both AS80 and AS150 show maximum depth of corrosion attack less than 200 µm compared to 22MnB5 of 900 µm. AS150 displayed better resistance to cosmetic corrosion than AS80. AS80 coating shows higher resistance to red rust pitting corrosion than AS150. E-coat thickness of 15 µm results in higher resistance to redpitting corrosion than lower e-coat of 8 µm.