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.
|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.
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.