Got rust in my 357 mold cavity.

[gwozdz]

I did a search and a few people talked about naval jelly to remove the rust. Does the naval jelly also etch and remove metal from the cavity thus enlarging it or if so is it neglegable? TIA

[OuchHot!]

The phosphoric acid in naval gelly principally attacks the oxide....but that rust can be pretty invasive so you may see alarming pits. PA will etch steel but at a slow rate. I do not think that normal application times will remove much base metal. Metallographers use PA to illuminate the grain boundaries on samples for microscopic examination and the attack is mostly the oxides and precipitaes between grains...not the grain itself.

[cbrick]

I've used naval jelly on a mold and was pleasantly surprised at how well it worked. It can leave pits in the cavity if the rust is deep enough. I wouldn't leave it on any longer than really needed, rinse well after with alcohol or some such to be sure it's all gone. I may have gotten lucky but I used it on an old mold that was in a box of stuff I bought and figured I had nothing to lose. It saved the mold and all was well.

Rick

[gwozdz]

Thanks guys. I'll give it a try as soon as I can find some.