Steel A131: marine-grade hull steel

To clear up a common misconception: Steel A131 does not belong to the category of "weathering steels." Its chemical composition does not rely on copper, phosphorus, or chromium to enhance corrosion resistance; rather, it is a carbon-manganese hull steel. Its "marine corrosion resistance" is achieved through specified corrosion allowances and protective coating systems, not through the inherent corrosion resistance of the material itself.

Corrosion rates vary significantly across different parts of a ship's hull. In the splash zone—characterized by alternating wet/dry cycles and an abundant oxygen supply—local corrosion rates can reach the order of 0.1 mm per year. The fully immersed zone follows, while the seabed sediment zone is dominated by an anaerobic environment. Common structural standards mandate specific corrosion allowances for each zone. Furthermore, ballast tanks must meet stringent coating performance standards; corrosion occurring at damaged spots in the coating is often more hazardous than uniform thinning of the steel.

BBN Steel supplies the full range of A131 hull plates. We can manage negative thickness tolerances based on project requirements to ensure the net thickness remains sufficient after accounting for the specified corrosion allowance. We also offer shot-blasting and the application of shop primers. When requesting a quote, please specify the required corrosion allowance, coating requirements, and the intended operational zone so that we can accurately calculate the necessary order thickness.