Ultra-High-Strength Hot-Rolled Structural Steel as Paint Substrate and Engineering Material

Mikko Arponen, Rautaruukki Oyj, Finland and Ari Vaha, Teknos OY, Finland

Increasing environmental requirements and cost efficiency have led to more stringent specifications for the fuel consumption of vehicles and lifting, handling and transport equipment. Consequently significant weight reductions and better designs are needed. These demands mean thinner materials and typically the use of ultra-high-strength steels. As well as uniform mechanical properties, the use of high-strength steel requires good corrosion resistance since the importance of corrosion damage increases as material thickness decreases. High-strength steel with inherent corrosion resistance is well suited to painting, as the life of the coating is clearly better when the corrosion resistance of the steel is improved by special alloying.

This paper describes the development of ultra-high-strength steel with excellent corrosion resistance together with good mechanical properties. The improvement of corrosion resistance is based on weathering steel type alloying with Cr, Cu and Ni. The influence of steel corrosion resistance on paint film durability in different atmospheric conditions is discussed. The corrosion properties of bare and painted steel specimens were tested with conventional electrochemical salt spray laboratory tests as well as with outdoor tests.