I have told this story before. Eight years ago, I bought a used NF 12-42 BR model. A year later discovered it would not hold track properly. Called NF, told them it was used, and the nice lady said just send it in and we will take care of it. Sent it with a letter describing the problem and told them again I bought it used. About 7 or 8 days later, the brown truck was at my door with the scope. NF repaired it at no cost and even paid the return shipping. Best warranty on the earth!!!
I would be concerned about ceracoting a scope. Might br possible, but the internals are so delicate that I would not take a chance.