bobmct wrote:

I've tried just about everything I could think of to remove this
scale without success including white vinegar solution.

1) lacquer thinner (right next to the paint thinner / varsol on the
shelf of your local hardware store. Gasoline, toluene, acetone
or nitro-methane might work if lacquer thinner fails. The use
of these solvents would be advised if the scale is the result of
some sort of paint, glue, caulking, sealant, etc.

2) a 50:50 mixture of water and muriatic acid (hydro-chloric acid)
soaked into a paper towel and applied by hand (wear gloves if
you're thin skinned). Muriatic acid can be bought in gallon-
sized jugs at Home Despot and other big-box hardware stores,
and probably also pool supply stores (might be called "shock").
Use of acid would be the way to go if the scale is a mineral
deposit of some sort.