Grmps,
Good question, but unfortunately, ...I have no answers to this one.
I have several concerns about such temperatures
1. What oven would be able to heat to 250C . Most wont unless designed for running at such high temperatures.
2. What also would the effect be on the alloy? My understanding on alloy with elevated heat is, that the composition may start to "bleed" on the surface with separation of the various metals.
I have no idea, what such surface change on alloy would result with coating and bond.
It is possible, that coating may withstand short heat such as for 15 minutes at 250. However, I do not know any one that has carried out such experiment. The only way is to try the experiment. Most colours will be severely changed.
For the coating and application, why would any one need such high temperature conditions, when good results can be obtained at a much lower temperature conditions?
A couple of commercial manufacturers, in fact fast cure the coating at about 220C, for about 4-5 minutes to increase production rates. But that is the highest temperatures that I am aware of as being used.
As I have said, the setting and bonding of the coating and alloy both needs to get to 180C and held there or nearby for an extra 3 minutes to finish. (generally with oven around 200C)
Having oven at 250, you would possibly get alloy to that 180C in very quick time.
Also, it will be difficult to control exact reproducibility for each batch as a few seconds either way in oven may change results.