I have used POR-15 with great success on my IRS a few years ago.
Powder coating tends to crack and is not suitable for the IRS frame itself. In my opinion,
Hammerite is a very overrated product that does not provide very good protection. In contrast to Hammerite, POR-15 provides an extremely hard and strong surface and is far superior in terms of rust protection.
The disadvantage of POR-15 is that you have to follow the instructions very carefully, including thorough degreasing and using POR-15 Metal Prep first, which is an etching solution. Here in Europe it can be a bit difficult to buy POR-15, but I found a dealer in Germany
https://www.por15.de.
Jay Lenno made a video about POR-15 a few years ago
