German steel protection specialist Steelpaint reports that the increasing adoption of hydrojetting in the global ship repair industry is driving demand for coating systems capable of performing on surfaces that challenge conventional two-component paints. The shift comes as shipyards worldwide face tightening environmental regulations on dust emissions, waste disposal, and runoff containment, making traditional abrasive blasting methods costlier and harder to permit in many jurisdictions.

Hydrojetting—also referred to as water jetting or water blasting—employs ultra-high-pressure water at 700–1,000 bar to clean, descale, and strip coatings from hulls, decks, cargo holds, and tanks. It has become the primary alternative to dry grit blasting during drydock maintenance, which faces growing scrutiny over its environmental impact on surrounding marine ecosystems.

Unlike abrasive blasting, hydrojetting produces no dust or spent abrasive material and significantly reduces contaminated waste released into the environment. However, Steelpaint notes that it also introduces difficulties for conventional coating systems. Because hydrojetting does not create a new anchor profile on steel, residual moisture and flash rust can compromise adhesion and curing, according to Steelpaint technical director Andreas Engert. This is a critical gap, as corrosion-related maintenance accounts for a significant portion of vessel operating costs, and coating failures during service can necessitate costly unscheduled drydockings.

Traditional coatings can struggle to perform reliably under these conditions, particularly in hot and humid climates where relative humidity frequently exceeds recommended application limits.

"If conditions are not ideal, such coatings can fail to adhere properly, blister, crack or break down," Engert says. "Single-component moisture-cure polyurethane coatings like our Stelpant and Stelcatec systems can overcome these limitations."

Engert explains that this category of coating system can be applied at relative humidity levels of up to 98% without dew point restrictions and is suitable for damp surfaces and areas exhibiting light to medium flash rust. The coatings are also engineered to maintain strong adhesion on partially corroded or relatively smooth steel surfaces.

"These single-component coatings are well suited to onboard maintenance, where conventional surface-preparation standards are often impractical," he says. "These coatings require no mixing and can be applied by brush, roller or spray to damp or manually prepared steel."

Designed for temperatures ranging from -5°C to 50°C and relative humidity up to 98%, the coatings adhere to all types of steel—including stainless, galvanised, and aluminium—enabling corrosion protection work during drydocking or while vessels remain in service.

"Single-component moisture-cure polyurethane coatings can be applied to hydrojetted steel prepared to SSPC-SP WJ/NACE WJ (WJ-3 – WJ-2) standards, as well as vapour-blasted and manually or power-tool prepared surfaces," Engert says. He adds that steel coated with a moisture-cured system and prepared only by high-pressure hydrojetting can deliver "better long-term performance than conventional materials applied to more extensively prepared substrates."

Hydrojetting has gained particular traction in settings where waste disposal, environmental controls, or operational constraints make abrasive blasting less feasible. Steelpaint highlights government-owned shipyards in China, which have broadly adopted hydrojetting as their preferred steel surface preparation method. The trend extends beyond China: shipyards in Europe, the Middle East, and parts of Southeast Asia are increasingly adopting or evaluating hydrojetting as environmental compliance costs associated with grit recovery and disposal continue to rise.

Steelpaint director Frank Müller said: "By combining hydrojetting with moisture-cure coating technology shipowners and offshore operators benefit from an alternative corrosion-protection method that can simplify maintenance, reduce maintenance costs and extend service life in demanding conditions."

He continued: "Sustainability goals are optimally supported, as waste is reduced and resources are saved during surface preparation, additionally the single-component properties of the coating material also reduce waste due to less packaging."

Additional advantages are evident in labor efficiency, as the mixing process required for conventional two-component products is eliminated. Because single-component coatings have no pot life, waste from mixed but unused two-component product is also further reduced.

Steelpaint's moisture-cure coating technology has been in commercial use since 1982.

Source: Steelpaint GmbH