Duralac Anti-Corrosive Jointing CompoundIf you have used a metal fastener through a hole which you have drilled, or used a fastener which drilled itself. Without realising it you have started a process of corrosion. When two dissimilar metals are brought together, an electrolytic process occurs. The US aerospace industry recognised this and did something about it. They developed an anticorrosive jointing compound called DURALAC. This product is used religiously, in the marine and aircraft