Soak sill plates in vinager?

[Great Lakes Greg]

I soaked my sill plates in vinager over night. It took care of all the crud around the Ford script, but there is still discoloration in the metal. I don't think it is corrosion because I can't feel it when I run my finger across it.
Is there another recipe, or perhaps I should get them plated?

 

[Craig Lewis]

Have you soaked them in lacquer thinner to get rid of any non organic coatings?..such as oils,paint,clearcoat,wax,etc.
After lacquer thinnner and a scrub with a stiff brush, go back to the vinegar and it will etch the whole service evenly. I'd be cautious soaking too long in the vinegar though. You're going to end up with a grainy surface as it eats away.
I don't believe they were plated. Some of my originals appear to have a shiny grayish coating, but I always thought it was some type of old paint.
Maybe one of the experts will help us out here??