There are 2 surfaces where rust is a concern. The unison ring and the turbo body on which the unison ring slides. Typically the turbo body gets so pitted that the sliding of the unison ring is inhibited, causing the problems and not the unison ring rusting. I wonder if a ceramic coating could be applied onto the the turbo body. That along with a stainless steel unison ring would REALLY get rid of the issues with a VGT.