Rust Killer,anyone - Updated job done/ Not done

[fazersharp]

“Max temperature 315°C (<100 continuous)” according to the manufacturers.
The pipes there will be over 100ºC (though under 350º).. I wonder how long qualifies as continuous?
Still, it can be done in-situ so if it does fail at least it won’t be effort wasted.

I used and still have some gun gum left but half of that has fell off, as you can see I did prep the area well. I dont mind giving chem metal a try and then I can use whats left over on other jobs