I'm obviously not a boiler person but the "absolute must" line and ashes are incredibly "corrosion" line just turn me off in general.
I have been using it, but only because a container of it came with my new 560 HDX. I do not plan to buy any more after this runs out. It seems that if you keep the moisture out of the firebox that the ash should not be a problem.
My guess would be yes, if it can withstand the temperature. When you add lime to your soil what does it do ? Heatmaster, Crown Royal, etc, etc don’t peddle these products to their customers and the boilers seems to last just as long or longer.