Depends exactly what the "rust converter is" - for example if it's a chelation agent, which removes the iron from iron oxide, then it may be a reasonable thing

Depends exactly what the "rust converter is" - for example if it's a chelation agent, which removes the iron from iron oxide, then it may be a reasonable thing to use. I will say - while there is plenty of stuff that will turn rust black, but what they describe sounds does in fact sound like a chelation agent (like evaporust or rust-911) used on rust. The result will often look black because it is no longer iron oxide. The article makes it sound like they are simply concealing, but chelation is not cosmetic - it is a chemical process that removes iron from iron oxide (because it is weakly bonded), but not from the rest of the metal. It will not corrode further from the "rust", because it is no longer rust when it is done. (it still obviously has to be protected from corrosion again, but ... The other part is that it's unclear what state they are delivered to peloton in from the supplier. If they are bare steel still, it would be perfectly normal to occasionally get rusty steel and have to clean/prep it prior to painting. Usually it is VCI protected/etc, but this is not perfect. It would be ridiculous and wasteful to reject bare steel parts because some of them are cosmetically rusted and need to be cleaned up. It's not possible to find iron/steel that doesn't have some oxide present. The only question is how much. If they are supposed to be delivered powder coated or whatever, normally it should not be rusted. This would be more concerning. Some of the article reads like nonsense - like they say "some that were sold were rusted internally". I'm not sure what the person quoted actually said (hopefully not that), but that's literally not possible as described. Iron oxide, as one might expect, requires oxygen. It can't rust inside-out. Maybe they mean that there are rusted parts inside that are no longer accessible or something.