Traditional Ship Coatings Struggle To Prevent Corrosion After Hydrojet Preparation

German ship protection firm Steelpaint reports that the increased use of hydrojetting in global ship repair is driving demand for coatings that can adhere to surfaces prepared by the high-pressure water technique. Hydrojetting, also called water jetting or blasting, blasts hulls, decks, cargo holds and tanks with ultra-high-pressure water (700-1,000 bar) to clean, descale and strip old coatings.

Unlike abrasive blasting, hydrojetting leaves no dust or abrasive waste, but it can create issues for traditional two-component paints.

Steelpaint's technical director Andreas Engert explains that hydrojetting leaves residual moisture and flash rust on the steel surface, which can hamper the adhesion and curing of conventional coatings. This can be especially problematic in hot and humid climates where humidity levels often exceed recommended limits. Engert highlights that single-component moisture-cure polyurethane coatings like their Stelpant and Stelcatec systems can overcome these challenges.

These advanced coatings can be applied even at high humidity levels up to 98%, without restrictions by dew point, and are suitable for damp surfaces with light to medium flash rust.

Engert notes that these single-component coatings excel in onboard maintenance, where traditional surface preparation standards are often unfeasible. They require no mixing and can be applied by brush, roller or spray to damp or manually prepared steel. They are effective on various steel types, including stainless, galvanized and aluminum, enabling corrosion protection during drydocking or while the vessel remains in service.

Steelpaint's Engert states that coatings 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, can deliver better long-term performance than conventional materials on more extensively prepared substrates.

The firm points out that hydrojetting is particularly favored in government-owned shipyards in China due to waste disposal, environmental controls or operational constraints that make traditional abrasive blasting less viable. Frank Müller, Steelpaint director, explains that combining hydrojetting with moisture-cure coating technology offers shipowners and offshore operators an alternative corrosion-protection method that simplifies maintenance, cuts costs and extends service life in demanding conditions.

This approach also supports sustainability goals, as it reduces waste during surface preparation and minimizes waste due to the single-component properties of the coating material.