How to Repair and Protect Sea Water Pumps (With GIFs) 

Pump cavitation happens when the local pressure inside a pump falls below the liquid’s vapor pressure. This pressure drop causes the formation of tiny vapor bubbles – typically around the pump impeller or inlet areas. As these bubbles move into regions of higher pressure, they suddenly collapse, generating intense shock waves that physically erode metal surfaces. Belzona offers targeted solutions to repair and protect pump components from cavitation:  

Belzona 1111 (Super Metal): This is an epoxy paste that can rebuild damaged metal areas, restoring the pump’s original profile prior to application of a Belzona coating.    

Belzona 2141 (ACR‑Fluid Elastomer): This is a flexible, cold-applied polyurethane elastomer designed for ultra-high-velocity and cavitation-prone areas. It provides exceptional abrasion and cavitation resistance, with proven performance at water velocities up to 115 knots.    

A water pump functions by creating a pressure difference that moves water from one location to another. Most common are:  

1. Centrifugal Pumps 

A motor spins an impeller and the curved vanes fling water outward via a centrifugal force. This rapidly spinning motion generates low pressure at the centre (eye), pulling more water in, and high pressure at the outer edge, pushing water into the volute casing and out through the discharge pipe. The volute casing then converts some of the water’s kinetic energy into static pressure, enabling continuous flow. 

2. Positive-Displacement Pumps 

These use mechanical means (pistons, diaphragms, screws, gears) to trap a fixed volume of water and push it out. Positive-displacement pumps are ideal for applications requiring a constant flow regardless of pressure.     

3. Other Types 

Submersible pumps: sealed motors submerged in water, often multi-staged centrifugal types.  

Hydraulic ram and Archimedes’ screw pumps: use flowing water or screw motion to lift fluids.  

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When corroded or eroded, water pumps can be rebuilt with Belzona 1111 (Super Metal), then coated with Belzona 2141 (ACR‑Fluid Elastomer). The combination of these Belzona systems restores the surface profile, protects the substrate from corrosion and cavitation – all while prolonging equipment life and mitigating maintenance needs. In turn, this significantly lowers the cost of running the pump, enabling asset owners to minimise their financial expenditure.

Choosing the right sea water pump depends on your vessel’s system, flow requirements and corrosion resistance needs. Several top-performing brands are widely recognised: Grundfos, Desmi, Tsurumi, Jabsco and Sherwood. Belzona polymeric repair and protection systems can be applied to all of these pumping systems, increasing efficiency and minimising the need for pump replacement.   

Case studies show that pumps that have been repaired and protected with Belzona polymeric technology last up to three times longer than untreated ones – making repairs highly cost-effective relative to full pump replacements.       

Yes, Belzona systems have gained the following global marine approvals: Lloyd’s Register, ABS, DNV, RINA, China Classification Society, Korean Register, and more.