Spiral Wound gaskets can be fabricated of any metal which is available in thin strip and which can be welded; therefore they can be used against virtually any corrosive medium dependent upon the choice of the metal and filler.
Theoretically, it is no longer contagious when there is no more fluid leaking from the sore, and no new blisters are forming. However, I always assume that a cold sore is contagious until it is completely healed, and to the best of my knowledge I've never transmitted the virus to anyone else. Abreva is a very good remedy. If applied when you first feel the tingle you can actually prevent the cold sore from erupting into blisters.
Canker sores are not a form of herpes, however, they are often confused and mistaken as herpes. Canker sores are not considered to be contagious. Cold sores and mouth herpes on the other hand are caused by the herpes simplex virus and can be very contagious. Canker sores usually occur inside the mouth, are gray in color and have a distinct edge. The sores will usually heal within 10 to 14 days, without treatment.