OSPHO (Ace Hardware) and Prep & Etch (Home Depot) are the same basic product .... Phosphoric Acid but not a high % version ... thus can be sold for consumer retail uses. You can get a much higher % version via several chemical supply companies, but the price is much higher per gallon. I checked and could get a 10 gallon tote with 60% mix (versus less than 10%) but it was near $400 delivered.

Nearly all the rust conversion stuff is some variety of phosphoric acid and can work nicely as a wipe on and remove material, but for heavy rust, the best method I have found is to do a complete dip process. For things that can fit in the various containers I use, even just an hour in the straight OSPHO will do the job when the rust is not super bad. Overnight will take care of the worst stuff, and give you a very clean new metal look. It is best to either prime the water rinsed part asap with one of the 2 part primer/ sealers, or a quick wipe of OSPHO will give you an almost copper green look over steel. No rust will redevelop after the wipe and dry process. The cautions I've been give though is that some of the "direct to metal" primers may not like the OSPHO residue, and won't stick well. Others may know more of how that all goes. One note of the prices ..... I got the Prep & Etch for $15 / gallon at Home Depot ... OSPHO was about $22 at Ace. Same % stuff too!

One other rust remover that works if you have the patience to use it ... is molasses at a 20% mix with water. I'm currently dipping an F1 grille to rid it of rust in all the rather tough to reach areas. Takes about a week if the rust is not too bad, 2 weeks + for nasty stuff. It does not work to remove paint though ... so that has to be done first. Just be sure to use the molasses outside ... gets a little smelly to use in the garage ... especially bad if connected to your house. SWMBO will object!!!!

I'm using the molasses simply because it is so much cheaper to use when I needed to fill a 100 gallon cattle watering trough as my dip container. OSPHO would have run me $1500 ... the molasses was $100 for enough to make up the 20% mix. Slow but cheaper works for the larger parts that can be dipped.

RG in Spokane

 

Thanks Guys,
robertr I just read about using molasses with vinegar! funny that you mention it! I never use molasses for anything but oatmeal!
I was a kid living on the farm and there was a molasses for the cows, in a big tank it had these knurlized wheels the cows would lick the wheels...anyway my point was that I don't think my city folk nieghbors would appreciate it! I miss living in the country...can't even pee outside here!

 

Hey I was at the paint store today and was checking out that CHASSIS SAVER. $110 ish a gallon. there were a couple guys talking about how good the stuff is and good words about it on here as well. Thinkin that may be the way I go. so it like POR-15. are there other of brands(cheaper?) I know you get what ya pay for but....

 

You won't need a full gallon to do that cab bottom. Just to give everybody an idea of how far it goes, I painted my entire frame on my F1 with less than a quart of that Chassis Saver paint. I used a bag of those cheap dollar store foam brushes in the process. And one more thing, the guys who sold it to me kept stressing--DO NOT shake it when mixing. Just open the can and stir it with something.

 

Yeah i suppose that shaking it up puts air bubbles in your finish...makes sense to me...