Transformers-Tin Coated
Usually there is a thin layer of varnish applied to each lamination prior to assembly. I've reassembled transformers that I rewound and I dipped each piece in polyurethane prior to reassembly. The isolation doesn't have to be perfect, but any metal-to-metal contact will allow eddy currents to increase.
The most common solution regarding this matter is repainting the exterior coatings that will prevent the transformers from being damaged due to corrosion. ... A lot of equipment pieces within a substation are also vulnerable to corrosion, and these could fail eventually when neglected.
