Aremco Products (Valley Cottage, NY) offers Pyro-Putty, a high-temperature sealer and metal repair compound. According to the company, it is now used to bond and repair cast iron and steel components used in automotive, truck, marine, and industrial applications to 1600 degrees F (871 C). Pyro-Putty 2500 is used to bond, seal and repair defects up to 1/4" in cross-section in cast iron and steel components and structures. It can be lightly machined then painted after curing, and the product is available from stock in pint, quart, and gallon containers.
Check out www.aremco.com to learn more.