Wash the chain, dry it, rub it down with graphite then you will have to raise the temp accurately enough to about 1450 then quench it until cold in water or mineral oil, there are also special quenching oils out there too. Reprocess with heat to about 450F for about 15 minutes and let air cool, then after cool lubricate with silicone oil, reheat to 350f and let cool, lubricate again, reheat to 350f and let cool, and then lube with light chain oil.

The silicone will burn off and oxidize forming a barrier on the surface so it is resistant to rusting.