Corrosion resistant steel approval

05 Feb 2015

ClassNK has issued approval for Nippon Steel & Sumitomo Metal Corporation’s newly developed corrosion resistant steel (NSGP-2) for use on the upper deck and/or inner bottom of crude oil tanker cargo oil tanks (COT).

This is the first time that approval has been granted for corrosion resistant steels for both the top and bottom parts of the COT, providing owners and shipyards with a full and practical alternative to coating systems.

Yasushi Nakamura, executive vice president, ClassNK, said: “While coated conventional steel meets IMO regulations, the additional costs associated with coating application can be high. This approval of NSGP-2 means that owners now have a practical alternative to meet IMO regulations for COT corrosion protection, and we expect the use of this kind of steel will increase in the future.”

Because the use of corrosion resistant steels should allow shipyards and owners to significantly reduce the time and cost related to coating application, development of such steels has been a topic of intense research over the past several years.

However, differences in the corrosion mechanism found in the top portion of the COT, which is exposed to gases released from crude oil during transport, and the inner bottom, which is in direct contact with the crude oil cargo, have always presented a major challenge to steel makers.

Nippon Steel & Sumitomo Metal Corporation released the world’s first corrosion resistant steel (NSGP-1) for use on the inner bottom of COTs in 2011.

And now NSGP-2 is expected to significantly lessen the financial costs associated with applying protective coating to conventional steel during ship construction and after going into commission.

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