a question about my evaporator

[The dairy farmer]

I had my first boil on my half pint evaporator last night had a couple problems but got it worked out,
my question is I firebricked my arch but in some spots the galvinised metal turned white and was extreamly hot unlike the other spots,
it was right next to the chimney pipe hole is there anything in can do it is all covered by fire brick except for a 1-1/2 inch gap around the top
I can post pictures if it would help ??

[Sundown]

I also have a half pint. Get a bag of refractory cement or a can of the premixed stuff and trowel it into any of the openings between the brick and around the smokepipe outlet. I mortared all of my brick in with firebrick cement and it has held up good for four seasons. I don't recall the temperature rating of the stuff I used, but it was high end of what is available.