Primarily Petroliana Shop Talk Forums Shop Talk Petroliana Forums General Petroliana Discussion Cleaning rust that is 'on top' of porcelain

I have used muriatic acid many times, and I never wet the sign first. Apply it right to the dry finish and let sit for a few minutes and then rub with something soft. I usually use a rolled up paper towel.
Heres 3 pictures of my porcelain 36B door.
First picture is the before picture.
Picture 2 is during cleanup.
Picture 3 is the finished product!
Need I say more?