I have been using a product called "Metal Rescue" available @ Menard's for ~$25/gallon. Part #WH290487 Been happy with it for rust removal on cast iron parts. I believe it is a 'chelation' (?) process product. Enviromentally friendly, low health risk, no special requirements for disposal. Chelation only dissolves the rust. Only downside I know of is that temperature of the solution & exposure time of the part, BOTH have to be closely controlled. Their Web site is:
www.workshophero.com There are also some other chelation solution products available as concentrates. I have not used any yet. But you don't pay the high $/gal price for the dilution water or the shipping cost of the added water. The concentrates must be diluted with water to activate them.
I am much happier with this than the acid based products I have used before. With acid it is VERY difficult to neutralize the action; it is hazardous to humans, pets, flora, etc; and can badly damage iron parts if over exposed. The fumes from acid solutions can rust everything in your shop. The other problem is acid desolves everything.
I have also used alkaline based 'hot tank' solutions when I worked at auto machine shops. They work well when new, but after removing a lot of grease & gunk, the derusting aspect is compromised. There used to be high alkaline content 'rust digesters' (essentially concentrated hot tank solution), but I understand they are no longer available. Outside of a 55 gal drum with a drum heater, alkaline solutions dont' work well in a small unvented shop. And, as above, hot tank fumes can rust everything.
There is a lot of info out on the web about derusting iron & steel. "Caveat Emptor" I use something easily replaced or that I am willing to sacrifice when working with a new process...............
Hope this helps,
Fordboy
