Cold-Cure Rebuild of a Corroded Marine Propulsion Shaft
Industry: Marine (MRNE)
Application: MPT-Mechanical Power Transmission (MPT)
Substrate: Carbon steel
Customer Location: Croatia
Application Date: October 2014
Products: Belzona 1111 (Super Metal)
Problem: During an inspection of a commercial fishing vessel, heavy localized corrosion was discovered on the carbon steel propulsion shaft. The damage was situated exactly at the seal journal—the critical interface that maintains a watertight barrier between the ocean and the vessel’s interior. If this corroded profile were left unaddressed, it would inevitably tear the seal, leading to seawater ingress into the hull. The vessel owner required a rapid, reliable solution to prevent a catastrophic leak without incurring the massive costs associated with prolonged dry-docking.
Application Situation
During an inspection of, heavy localized corrosion was discovered on the carbon steel propulsion shaft. The damage was situated exactly at the seal journal—the critical interface that maintains a watertight barrier between the ocean and the vessel’s interior. If this corroded profile were left unaddressed, it would inevitably tear the seal, leading to seawater ingress into the hull. The vessel owner required a rapid, reliable solution to prevent a catastrophic leak without incurring the massive costs associated with prolonged dry-docking.
Application Method
The shaft was extracted and mounted onto a lathe for a precision repair. To prepare the area, the corroded seal journal was undercut via machining to remove the damaged metal, and the surface was thoroughly roughened to ensure an optimal mechanical grip for the repair composite.
While the lathe rotated at a very low speed, Belzona 1111 was applied. To prevent air entrapment and ensure maximum adhesion, the first layer was aggressively scrubbed into the roughened profile using a short-bristled brush. The composite was then built up in thin, consecutive layers until the outer diameter slightly exceeded the shaft’s original dimensions. Once the Belzona 1111 had fully cured, the shaft was machined back down to the exact OEM tolerances and given a final polish with emery cloth to ensure a perfect mating surface for the new seal.
Belzona Facts
Attempting to repair this damage using traditional weld overlay would have introduced extreme heat, almost certainly causing a shaft of this diameter to warp and distort. Correcting that thermal stress would have required shipping the shaft to an off-site facility for specialized heat treatment (baking and slow cooling) prior to final machining.
By utilizing the cold-applied Belzona 1111 system, the maintenance team completely bypassed the need for hot work and thermal stress relief. The entire repair and machining process was successfully executed in a single day, eliminating costly shipping delays, minimizing dry-dock fees, and allowing the vessel to return to its revenue-generating operations.
