Figured I might find help here from someone that has experienced this before. I am doing some light reconditioning of some iron cylinder heads. Main issue was pitted valves that I have replaced and lapped. I attempted to clean these heads afterwards before bolting back on the car. My method of cleaning the heads was to use an old dishwasher. I know this has had mixed opinions, but I had seen a few videos that convinced me to give it a try, and it turned out pretty good. Now I knew the heads would have surface rust after the wash. Here is where things went kinda wrong. I knew of two options to remove the surface rust. A vinegar bath, and electrolysis. The latter which I had never tried but always wanted to. So I do some more research, it seems straightforward. I filled up a container with a mixture of water and washing soda, got the heads hooked to the negative terminal of a battery charger, and used a piece of s**** iron as a sacrificial anode. I left it overnight. I expected to pull out a nice new looking pair of heads. What I ended up having was a pair of very blackened cylinder heads that would only clean up with a lot of scotch brite. This has obviously created an issue as that black stuff (which I later found to be called magne***e) is in every p***age, valve guides and all. From further research, there seems to be no way to remove this stuff other than scrubbing it. I ended up cutting my losses and bought both heads to the machine shop to get sand blasted. So what happened? I've seen videos of people doing exactly what I did using iron rusty heads and they came out great. The only answer I may have found was that my tap water was to blame. That seems to make sense, but I wanted to see if anyone else had more input or experience on this.
Electrolysis works by line of sight, you'll have to get rods into each chamber and port without touching the head or it will fault out. A cylinder head is not a good application for electrolysis. Did you have your polarity correct? I've always used tap water and washing powder for electrolysis. No issue. The black crud and set up on the part for proper coverage turned me off to the process. As a side note, I've plated a lot of parts with nickel and zinc, using my own set up, not the Caswell ready kits. Pretty fun, giving some background on the amount of time I've spent dipping junk in electrified solutions. Now you can try to use vinegar or citric acid and see of it cleans off the crud.
It did pull most if not all of the rust off the cylinder head, especially in the water jackets. The polarity was correct, and the sacrificial metal was full of rust so what it was intended to do seemed to work. But yeah, the black oxide... I wouldn't have even minded the scrub down after if it wasn't almost impossible to get the runners and small crevices cleaned. My main concern was the valve guides. I used a soft bristled SS brush that you put on a dremel and that cleaned all the valve seats/gasket mating surfaces just fine, but I was not about to use that on the guides. I know they're polished and that's when I cut my losses and brought them to the machine shop. I guess lesson learned, but it was fun to finally get to try it out. Next time I'll experiment on less detrimental pieces. The limited discussions I can find about this black oxide/magne***e issue online was pointing in the direction of the quality of the tap water. That seems to be the only variable at play here that could be different from anyone else's setup. Some people claimed they had little to no black oxide and claimed it was because they used distilled water and that it's important to do so. Others claimed it's a gamble and sometimes you get a lot and other times you don't.
I'm not crazy about the texture blasting puts on heads along with the grit you might be exposing the engine to.
The proper term is “reverse electrolysis”. I’ve had great results so maybe double check the polarity.
Now that I'm thinking back to the parts I did, I never put cast iron into the tank. Not sure of that contributed to it. I ran that tank for a month or so, and broke it down, just preferred other rust removal methods. Don't look up electroplating, don't do it. Started with a penny and a battery then I messed with it all winter. Learned a lot, but spent a lot of time on it.
It could be the metal. Not sure if the cylinder head I used had some weird reaction vs the guides I've seen people have online using iron heads. Maybe just the luck of the draw. I'm sure there's a specific reason, but I am not well versed enough in chemistry to know. You know, I forgot all about DIY electroplating till you mentioned it, and you may have just given me another rabbit hole to go down and spend way too much time on. Those are always fun; like electrolysis, when it goes right
The guys on the truck board showed a couple of videos on it and about all you need are an old school ****og battery charger and a non-conducting container and a pretty well ventilated place and a few pieces of s**** metal for anodes Electrolysis Rust Removal | WoodWorkers Guild of America (wwgoa.com) This video is a bit long but well worth watching and got me hooked on the idea. Rust Removal by Electrolysis: Use in the Restoration of Machinery - YouTube
The "****og" battery chargers have a couple advantages, where the modern chargers don't really work as well as they might for what you're trying to do. They probably cost $5 at a garage sale. I like the "smart" chargers and use them, but sometimes old school is the way to go. I haven't tried electrolysis.
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