I did some acid. An acid bath that is. No bad trips the way I do it. I’m posting this in the engine section because I’ve mostly found it useful in preparing a cast iron intake. I also used it on a water pump last night too. I’d like to avoid discussing the merits of media blasting. We probably all agree that media blasting gets the best results when cleaning up old rusty part. The merits of an acid bath will be discussed here. I’m posting so that I can hear what other bolters on here do in these situations.
For years I’ve read posts on other forums where people submerge rusty parts in apple cider vinegar and wait weeks to get rust off. Me? Nope! I’m not gonna build big vats and buy gallons of cider just to wait and wait.
My methods are my own. I used an acid bath because I wanted to treat rust INSIDE passages in the intake that media blasting couldn’t get to.
***EDIT*** Here’s what I did. I cleaned grease and grime off of the cast iron 283ci intake. Stripped any remaining paint with aircraft remover and a pressure washer. Wire brushed any heavily rusted areas. The water jacket passages had some “tree bark” scale rust which I partly knocked off with long screwdrivers and rags.
Here’s what I did. I poured 3 gallons of cleaning grade vinegar into a large tub. I wanted enough to submerge the intake. Overnight soak worked pretty well but I wanted to speed things up a bit. So I added some already diluted muriatic acid to the tub. That sped up the process quite a bit. (I’ve used diluted muriatic acid before to wash out a rusty gas tank before sealing it with KBS tank sealer.) Another few hours and the intake was a nice even gray.
The second intake only took overnight, so the increased acidity definitely helped speed up the process.
Removed intake from the acid bath and rinsed with water and then a baking soda spray to neutralize all the acid. I was impressed with how much rust was removed from the cast iron, including the interior passages. I then used a propane torch to quickly heat and dry the intake to avoid flash rust. A little flash rust is inevitable. A hot oven would work just as well if your wife isn't home. I was very pleased. I then let it cool and finished with an even coat of high temp engine primer.
Did the same for the water pump. Should I be concerned about the pump bearing being exposed to acid? I don’t know. I’m thinking it’s a sealed bearing.
I submerged a rusty 283 rocker cover today too but I was NOT impressed with the results. I’ll have the rocker covers media blasted.
Be careful when using acid. Don’t breath the fumes. Wear old clothes. Never add water to acid . . . ALWAYS do it the other way . . . . Add acid to water! Neutralize it with a base prior to disposal, unless it’s vinegar, then just make cole slaw. Store bottles of acid away from metal building walls and away from areas where people, children or pets might get ahold of it.
