Belzona makes a variety of products for different purposes and different services. We used Belzona products to make repairs to damaged cases and heads. We use other products to coat new pumps to improve life on these parts or to increase efficiency. It is part of our specifications to coat bowls and columns on new cooling water pumps with a particular product. This allows us to use carbon steel or cast iron and still get very good life from these components.
I would offer one point of caution. The Belzona products may restore the surface and performance to a damaged pump. But, they will not restore the full pressure capability. If there is any doubt about the pressure boundary integrity, I would suggest pressure testing after coating to be sure.
I would expect a good repair to last indefinitely. The greatest risk is that the coating will be undermined by the loss of base material on uncoated areas. If the entire surface can be coated, this can be avoided. This might be easy for a head, but not so easy for a case. I would also caution to be very cautious about getting the coating on surfaces where it is not wanted. Some of these coatings are very, very hard and cutting them off can be nearly impossible. You need to consult with Belzona or a local distributer to understand the hardness, machinability of the different coatings.
Follow the application instructions carefully. Pay special attention to cleaning and priming to get a good bond to the underlying surface. If the surface is smooth, consider an aggressive sand blasting to give it a good profile for the bond. Mix the coating well. Allow the required time for hardening and curing. Curing can be accelerated by application of heat using a heat lamp.
Johnny Pellin