Definitely need. Insulating layer can be used as antii-corrosion coating! Do according to the design and painting specifications!
That depends on the requirements. Brushing paint is needed. I an engaged in thermal insulation material wholesale and construction (see name).
Rust-proof treatment must be done. Without special requirements, you can use epoxy rustproof paint for basic protection. For high demands, you should use zinc anti-corrosion paint.
It doesn't matter if you odn't brush rust-proof paint and ready mixed paint. If you have brushed rust-proof paint on seamless steel tube, it is OK without ready mixed paint, but it will shorten the operation life of the steel pipe.
