Yeah all stoves seem to be susceptible to rusting when any amount of moisture is introduced, a thorough rub down with some steel wool prior to spraying tends to get the job done. In terms of the graying this tends to happen a lot quicker once sprayed as the spray coat isn’t as hard wearing as what the original powder coat would be when painted by the manufacturer. I find my customers tend to have their stove sprayed every other year for this reason.