First Standards for Application of Corrosion Resistant Steels

ClassNK has developed and released the world’s first set of standards for the application of corrosion resistant steels to the cargo oil tanks of oil tankers. The new Guidelines on Corrosion Resistant Steel for COT are the first guidelines to lay out clear requirements for the application of the new steels, whose use was approved by the IMO’s Maritime Safety Committee (MSC) earlier this year.  

The growing volume of crude oil carried by the world’s tanker fleet has led to rising concerns over pollution of the marine environment, and the last decade has brought tremendous changes to the building and survey requirements for oil tankers. Along with the shift towards enhanced survey programs, double hulls, and ballast tank coatings, recent efforts have been focused on establishing corrosion prevention measures for the cargo tanks of oil tankers. 

Amendments to the SOLAS Treaty requiring such corrosion prevention measures were adopted at the 87th meeting of the MSC in May 2010, and from January 1, 2013 corrosion resistance measures will need to be applied to the cargo oil tanks of all crude oil tankers. Along with coatings, MSC recognized corrosion resistant steel as an acceptable corrosion resistance measure, and adopted the new “Performance Standard of Corrosion Resistant Steel” along with the amendments to SOLAS. 

Corrosion resistant steel was developed by Japanese steel manufacturers specifically to resist the corrosive environment found in cargo oil tanks, and the new steel promises to provide owners and shipyards with a lower cost alternative to coatings. By using corrosion resistant steels, shipyards can reduce the cost of the construction and coating process, and owners can reduce costs from coating maintenance and reapplication.

Although the effectiveness of the steels has been proved on vessels in service, and use of this new type of steel was approved by MSC in May, one factor preventing their widespread application has been the lack of clear standards for their application. According to Dr. Yoshiya Yamaguchi, a Manager in the ClassNK Equipment & Material Department who participated in the development of the new steels: “These guidelines fill that gap and make the application of these new steels practical for the entire maritime industry.”

ClassNK’s new guidelines describe the procedures for application of the new steel in great detail, including area of application, construction work and inspection procedures during construction, as well as the required contents of the technical file. As the new guidelines also cover the requirements for type approval of corrosion resistant steels based on the amendments to SOLAS, the guideline is expected to be of great benefit to steel manufacturers as well.