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Lloyd’s Explains New Tank Corrosion Reg

Friday, February 17, 2012

More items for Program/Project Management

Lloyd’s Register has developed guidance to clarify the coatings and other compliance options in new IMO regulations regarding corrosion protection of crude oil cargo tanks.

The International Maritime Organization developed the regulations in the wake of several incidents involving structural failure in oil tankers. The requirements, approved in May 2010, took effect Jan. 1, 2012.

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The new IMO regulations are designed to address corrosion protection in cargo tanks. Corrosion attacks on ship structures have remained a tenacious problem, despite advances in ship design and materials, Lloyd’s Register notes.

The regulations employ performance standards aimed at inhibiting corrosion in cargo oil tanks. The standards were made mandatory by an amendment to SOLAS: regulation II-1/3-11, Corrosion Protection of Cargo Oil Tanks of Crude Oil Tankers, adopted by Resolution MSC.291(87).  The regulation requires that cargo tanks of crude oil tankers be protected against corrosion.

SOLAS (Safety of Life at Sea) Treaty measures promote maritime safety by inspecting ship construction, specifying load limits, and standardizing the handling of freight containers. SOLAS measures apply only to shipping in high seas and do not cover warships, small cargo ships, fishing vessels and sail boats.

Ship Corrosion Challenges

Lloyd's Register, the maritime classification society and risk management group, has developed a guidance note to explain the options included in the new corrosion protection regulation, which applies to new crude oil tankers of 5,000 dwt or above on international voyages.

The guidance notes the continuing challenge of corrosion attack on ship structures—a problem that has persisted even through the most rapid advances in ship design and building technology. Several factors exacerbate the problem, Lloyd’s notes:

• Ships are larger and more structurally complex than ever, creating large surface areas that require protection and adding to the difficulty of accessing all areas to apply, maintain and inspect coatings.

• High-tensile steels have been used to reduce scantlings—a thickness reduction that may reduce the life expectancy of ship structures.

• Double-hull tankers, now favored for their improvement to structural integrity, significantly increase the surface area requiring corrosion protection.

• Newer alloys in increasing use provide better corrosion resistance than structural ship steels but increase the complexity of material coupling consideration, and require special attention to maintenance and suitability for particular cargoes.

3 Options

The guidance notes three options for any ship subject to the regulations: coatings, corrosion-resistant steel and exemptions for vessels built solely to carry cargoes that do not cause corrosion.

The new regulations require corrosion protection in the cargo oil tanks for the under-deck cargo space and the cargo tank bottom. However, the guidance notes, the corrosion mechanisms in each area are dissimilar and need to be treated accordingly.

The guidance on coatings includes testing and inspection requirements, compatibility issues, and application controls. For example, application of the coating system is subject to extensive controls.

The guidance also notes that the yard is responsible for preparing the vessel’s Coating Technical File (CTF), which is to contain the specification of the coating system applied, a record of the shipyard's and ship owner's coating work, and detailed criteria for coating selection, job specifications, inspection, maintenance and repair.

Comment from sasha bacic, (2/20/2012, 4:13 PM)

If a Classification society developed such guidance, this is an evident sign that thing has gone far too far in terms of cargo tanks corrosion! The effects of localized corrosion of tank tops is known for more than 25 years! Paint manufacturers (some of them, unfortunately not all!) recommended tank-top coating while at the same time the shipbuilders (all of them!) argumented against it, using very often fallacious argument. Shipowners weren't much better! Except few rare exceptions, all others neglected the question due to prohibitive builders requirements in terms of additional costs. Being involved since 1980 in shipbuilding and since 1985 in anticorrosive protection, only a hand-full of shipowners insisted to have quality coating aboard their ships, all others were complaisant with the shipbuilders! You think that I'm exaggerating? You thing I'm wrong? Here is just one of the unbeatable proofs: Have you not seen in all (or dearly!) of the Shipbuilding Contract, on the one of first three or four pages, the following sentence: "The vessel shall have the appearance of a new ship." It is not written that the coating shall protect against corrosion for at least five or six years without any breakdown but "that the ship shall looks like a new ship"! In other words, the shipbuilder shall deliver a ship which "looks beautiful" !! Nothing less, nothing more!! And, at least in 2012 (!!!!!), an Class decided to "detail guidance" on cargo tanks coating. Better late than never!!

Comment from Ben Johnson, (2/21/2012, 5:37 PM)

I agree who cares how it looks it needs to be sealed in protected condition. This would eliminate corosion and evident contamination.

Comment from Than Nguyen, (2/22/2012, 4:00 PM)

Corrosion is a global problem that has plagued buildings, monuments, equipment, and infrastructure for centuries. Every day scientists, researchers, chemists, engineers, and other professionals create revolutionary solutions to combat corrosion and protect vital assets from the damaging effects of corrosion-related deterioration and failure. Being in the military packaging industry, I know that the deterioration of concrete structures in certain environments due to corrosion may result in costly and inconvenient maintenance so we need to be preventative.