Theres a few more things to consider than "heat resistant paint",is their insulation over the paint, is there chlorides or salts present from the environment, generally at 120 C your in the "sweat range" for pipe, so you would want to use an epoxy phenolic, be careful if your insulating though as the water will sit in the insulation and wreak havoc you wont see until its to late.
we are trying to protect the pipe from getting rusted. The environment is not very salty but there is temperature of 120 C what is ur expert advises in this condition.
NORSOK M-501 will guide you to use of thermal spray aluminium for both atmospheric corrosion and CUI protection, but for pipe of DN 50 and below, coating is possibly not the optimum solution.
You said that you are trying to keep the pipe from getting rusted.
Based on you provided information the pipe will be 120 degrees C ( 248 degrees F)
Water boils at 100 degrees C (212 degrees F) so any rain will rapidly "Boil" off and the pipe should remain relative dry. There should be little to no rust beyond what forms before the plant is started up and reaches full operating temperature. Normal high temperature primer and top coat should be all you require.
Unless you live by the ocean, finding a TSA applier for the relative cost of paint would be impossible, and unnecessary. Epoxy Phenolic is what you want (assuming this is carbon steel)
If its a stainless then no need to paint.
