Well fellas, Last year I built my shop heat exchanger using a tractor radiator(new one I had laying around) . Worked great for a year, couple of weeks ago furnace calling for water. Me thinks ut oh, where's the leak. I go hunting to find what I thought was a drain fitting leaking on the radiator. Had not been in shop for a couple of days and went out to find the floor wet. Upon further inspection, I found that all the rows of the radiator were leaking and looked like swiss cheese, joints were all leaking too. Chemical says safe for aluminum, copper, etc. Then someone pointed out the Chinese thing. I guess they use a solder that appears gold, USA stuff looks silver. Well I ended up ordering a new heat exchanger to replace that radiator. This time a USA piece. My advice is to buy the USA/Canadian stuff and save in the long run. I might add that the USA made heater core that I used ( it was used also) is still perfectly fine, no issues.