In general odors from very hot pipes and/or radiators are due to dust dirt or paint. It seems odd that they would be galvanized; perhaps that is an issue.

When I bought my house the steam radiators had sat unused for years while the house was heated by wood-burning stoves. I had a new gas furnace installed and the radiators were put back in use (some had to be reinstalled).

I was warned by the installers that I was at risk of the pipes and radiators leaking after being unused for so long... especially since I didn't know their history... and they recommended that I *not* drain the system because it can introduce air or problems somehow?! However, I thought they had a terrible "old pipe" smell, so I decided to drain some water from the boiler regardless. The water came out FILTHY and smelled exactly like "old pipes"! Hence, every now and then, I'd drain about a gallon of water from the boiler. Over time I noticed the clarity of the water improving and the smell along with it.

Have you tried draining any water from your system?