Both "chromate" and "dichromate" can and do provide sufficient corrosion resistance. The chain has to be plated prior to application of either.
The chromate or dichromate cannot be applied directly over the steel chain. Newer chromates have been developed that are last hazardous to the environment when breaking down in landfills. It has more do do with how the chain is prepared and plated prior to applying the chromate that gives you a superior finish. Typically zinc is used. If I had a sample link of each I could do some kind of testing and determine exactly what is on it (foreign vs. domestic). Thickness of the plate underneath the chromate is a factor as well. Zinc is good because even when scratches exist that are through to the steel underneath, it still supplies corrosion resistance because a galvanic reaction will take place whereby the zinc is sacrificial to the steel.
The chromate or dichromate cannot be applied directly over the steel chain. Newer chromates have been developed that are last hazardous to the environment when breaking down in landfills. It has more do do with how the chain is prepared and plated prior to applying the chromate that gives you a superior finish. Typically zinc is used. If I had a sample link of each I could do some kind of testing and determine exactly what is on it (foreign vs. domestic). Thickness of the plate underneath the chromate is a factor as well. Zinc is good because even when scratches exist that are through to the steel underneath, it still supplies corrosion resistance because a galvanic reaction will take place whereby the zinc is sacrificial to the steel.