Originally Posted by
elfmachine
Hello. I installed a SunRace CNM84 chain on my bicycle last year and after many months it rusted so much that it got stiff. Pretty strange that it rusted so strongly despite being plated with chrome or nickel. I didn't have time to lubricate it so I rode my bike with an unlubricated chain which became more flexible after a ride. Now removed the chan and placed it into a bath with phosphoric acid with zinc aka rust remover to remove rust before lubricating it with teflon wax. After a while I started hearing popping sounds and after chain inspection I noticed that many links had cracks! Did rust remover somehow cause breakage or cracks developed from riding an unlubricated rusted chain?
Phosphoric acid is a surface rust remover and should not be used in any kind of bath. The iron in the chain will react with the phosphate which is what lead to your cracking. I suspect that the chain also cracked near the name embossing on the chain plates. The embossing introduces some micro fractures that the phosphoric acid can utilize to get into the metal. That can lead to widening of the cracks and the ultimate failure of the chain. It will look similar to the cracking caused by salt in the picture from
this post
Although I would replace any chain that is has rusted stiff enough to not move any more, if you absolutely
have to remove rust, use
Evapo-Rust which is a chelating agent that doesn’t attack the iron in the chain. It’s far less hazardous than phosphoric acid and won’t damage parts.