A three-year coating trial aboard the 15,300TEU containership Maersk Hamburg has found significantly less corrosion and coating damage on a lashing bridge coated with Steelpaint’s moisture cure polyurethane coating system than on the same area protected with a conventional epoxy system.

The Steelpaint-protected area showed only minor corrosion and required no crew maintenance, while a competitor’s epoxy coating showed greater deterioration despite regular maintenance during the trial period.

In March 2023, Maersk Line applied the Stelpant coating and an epoxy system from Hempel – both of which included a zinc-rich primer and a topcoat – to lashing bridge Bay No.74 during Maersk Hamburg’s scheduled drydocking at Qingdao Beihai Shipyard, China.

The coatings were selected to minimise crew maintenance and avoid regular coating repairs in areas subject to heavy mechanical damage from twistlocks and lashing rods during loading/unloading operations.

Steelpaint’s system comprised 80µm of Stelpant-PU-Zinc and 150µm of Stelpant-PU-Combination 300, for a total film thickness (DFT) of 230µm. The Hempel system was based on 75µm of Hempadur Avantguard 750 and 175µm of Hempadur Mastic, for a larger DFT of 250µm.

The two systems were exposed to the same impact and operating conditions.

During an inspection at Xiamen Port in July 2026, however, inspectors reported 0.3% corrosion on the Steelpaint area, up slightly from the 0.1% reported after the first year of operation. Corrosion on the Hempel-coated area increased from 5% to 15% over the same period.

First-coat impact damage increased from 1% to 3% on the Steelpaint system and from 10% to 30% on the Hempel system. Second-coat damage increased from 10% to 15% and from 15% to 40%, respectively.

Significantly, the report notes that the epoxy coating had been regularly maintained by the crew, while the Steelpaint coating required no maintenance at all during the three-year trial period.

Steelpaint Director Frank Müller said the findings provide a clear indication of the long-term performance benefits of the Stelpant system.

“After three years there is almost no corrosion but there was significant corrosion and impact damage on the lower part of the lashing bridge protected by the epoxy coating,” he said.

“Where the topcoat had been removed, the Stelpant PU-Zinc primer remained intact. And where the primer had been abraded, 30-50µm of zinc remained attached to the steel with no corrosion observed. Under more intensive impact, around 10-30µm remained on the steel profile, with only very slight corrosion reported.”

The Hempel system behaved differently under impact. The report describes instances where the complete coating system peeled from the steel substrate, together with cracking and brittle coating behaviour. Where steel became exposed, corrosion was observed.

After three years, Steelpaint’s system measured DFT was 180-320µm, with the report saying there had been no significant change. The Hempel system measured 600-1,000µm after multiple touch-ups.

While a ten-year service interval is a viable projection, the inspection report does suggest that a Stelpant system could in fact substantially reduce, if not negate, the need to purchase sea-store paint for touch-up work. “This would reduce maintenance costs significantly over a ten-year period,” Müller said.

Another benefit, he said, is the higher sustainability of the Stelpant system due to the “significant reduction in VOC emissions” and the raw materials used.

Steelpaint already uses its coating technology in high-wear cargo areas on bulk carriers and container vessels but sees the Maersk Hamburg result as evidence of the coating’s wider commercial potential, especially in areas that are exposed to harsh corrosive climate conditions and mechanical impact.

“We have a significant number of references on bulk carriers, but box ships are vessel types where we would like to have more exposure,” Müller said. “The Maersk trial shows we have a very special coating for this sector.”