Mid-Life Polymer Recoating Projects Offer Clear Operational Advantages

Tank coatings are one of the most operationally critical, yet often underestimated, determinants of chemical tanker performance. For medium-range vessels entering mid-life, the commercial and environmental limitations of traditional cargo tank coating systems are becoming increasingly apparent, as market competitiveness depends on the ability to carry diverse, aggressive, high-specification cargoes.

A recent mid-life recoating programme involving six Ardmore Shipping product and chemical tankers, all approximately ten years old and originally delivered with epoxy-coated cargo tanks, provides a useful reference point. Owners increasingly report constraints trading aggressive cargoes such as methanol, free fatty acids (FFAs), vegetable oils, and certain biofuels using bisphenol phenolic epoxies and zinc silicates, which suffer from higher surface absorption and more intense cleaning requirements.

Recoating was carried out at Chengxi Shipyard in China using the MarineLINE® cargo tank coating system. The six Ardmore vessels involved include two South Korean-built 37,764 dwt D Class tankers, Ardmore Defender and Ardmore Dauntless, and four Japanese-built C Class vessels: Ardmore Cheyanne, Ardmore Cherokee, Ardmore Chinook, and Ardmore Chippewa.

At the core of the operational issue with traditional epoxy coatings is surface absorption, to varying degrees, cargo molecules can penetrate the coating structure, driving longer cleaning cycles, ventilation times, and higher energy consumption. MarineLINE®'s technical differentiation lies in the density of its cured polymer surface: heat curing creates a tightly knitted molecular structure comprising up to 784 cross-links, forming a chemically inert barrier that does not allow cargo molecules to permeate the surface once fully cured.

The operational impact of reduced absorption is most clearly seen during tank cleaning. APC estimates that a chemical tanker with premium epoxy-coated tanks carrying methanol may require seven to ten days for cleaning and ventilation before the next cargo; with MarineLINE®, this can be reduced to approximately three days. In fuel oil cleaning operations, where hot water washing and chemical treatments typically take two to three days, MarineLINE® can reduce cleaning time by up to a quarter.

Because the majority of energy consumed during tank cleaning goes toward heating water, faster cleaning cycles translate directly into reduced fuel consumption, lower emissions, and improved Energy Efficiency Operational Indicator (EEOI) performance, with a lower EEOI supporting stronger charter terms and higher daily rates.

The medium-range chemical tanker segment is emerging as a particular sweet spot for polymer coatings. According to APC's operational modeling, a 25,000 dwt tanker fitted with MarineLINE® can earn a considerable premium due to increased availability and cargo flexibility, operators trading in the spot market benefit directly from faster turnaround times, since faster cleaning and ventilation simply means more availability to take a trade.

MarineLINE® is currently installed on approximately 700 vessels worldwide, typically achieving a service life of seven to ten years in high-specification chemical trades, with some installations in clean petroleum product trades exceeding 20 years.