Thread: Ranex Rust Converter

Originally Posted by KevinB

Hi, I have treated some secondhand roofing iron with Ranex Rust Converter. Its active ingredient is phosphoric acid. Yep, it seems to have done the job. I did as the label said, brushing it on and wiping off the excess with handfuls of old rags. That was days ago. Today the metal is slightly sticky to the touch. My question is whether ( 1 ) I can brush on a coat of paint now, ( 2 ) I try to wash off the sticky bits, ( 3 ) wait for days or weeks or forever until the stickiness goes or ( 4 ) some other course of action. Woodworkers all, I have long appreciated your wisdom and your willingness to share your knowledge. Will someone help me with this, please? . . Kevin

You will find it very difficult to apply any finish to it with it being sticky like it is.

The stickness usually results from applying too much. Ranex contains a detergent which is itself sticky but it also absorbs water from the air which seems to prevent it from drying out. Left alone it may eventually dry out but sometimes it stays sticky for months. I try to do this oh hot days but if I don't have that luxury I usually dry treated pieces in a BBQ oven but you will need a big BBQ to do this. The other way is with a hot air gun but that is also impractical for sheeting

I have found that if ranex is diluted with about 25% with water it still works but dries quicker.

BTW Ranex is not a good product for anything galvanised.
While it converts rust into the more inert iron phosphate it will also dissolve the galvanizing off the unrusted bits leaving these less protected than before.

Thanks BobL . The area of the metal sheeting is not great. It's for a raised garden bed. I'll try the hot-air gun and see if that dries it out. Next time though I'll be diluting by 25%.

Thanks for your help - I appreciate it.

Regards,

Kevin

You'll find that Chemtech Rust-Off (also from Bunnies, but in the builder's oxides section) is about half the price and double the strength of Ranex (625 grams of phosphoric acid a litre compared to 300-odd).

Wet it and give it a bit of a scrub with a scotchbrite, then dry off with a squirt bottle of metho.

Thanks Master S - I have that noted for the next job. Cheers, Kevin.