OREANDA-NEWS. May 20, 2011. Sumitomo Metal Industries, Ltd. (Sumitomo Metals) has developed a new corrosion-resistant steel with tin (Sn) added that can be used in salt-containing environments, such as at the seaside or in cold climates where anti-freezing agents are sprayed. Bridges made of this new steel is expected to lengthen the intervals between repaints and reduce repainting workload.

1. Background for development
 In general, steel bridges are painted for rust prevention. As rust tends to spread from a scratch in the coating or a tip of materials, regular repainting is required. Lengthening the intervals between repaints or lightening repainting workload will result in reduction in maintenance and management costs for bridges.

2. Details of newly-developed steel
 Sumitomo Metals has found out the nature of the corrosion mechanism of steel coating in high salt-containing environments. We found out that in such environments, adding a trace of tin (Sn) can significantly improve corrosion resistance, and that this effect can be produced even if rust cannot be removed sufficiently during the repainting work. We were then able to develop this new corrosion-resistant steel with tin added, which at the same time satisfies more than similar basic performance properties(*) as conventional steel needed for bridges such as strength and weldability.

The use of this new steel enables to lengthen the intervals between periodic repaints, and to lighten repainting workload.

3. Future development
 As the new corrosion-resistant steel has high corrosion-resistant performance even with no coating, its application for bridges with no coating is also studied.

 Sumitomo Metals will carry out further studies on the longer duration between repaints and maintenance and the simplification of repainting work. We will thus contribute to cost reduction over the lifetime of steel bridges and savings in public work investment.