Advanced rust removal

[Hydratech®]

I have been working with a lot of chemistry lately in removing rust from vintage cast iron cylinder heads, engine blocks, intake manifolds, various parts... Electrolysis has been working astoundingly well, watching the solutions start bubbling and sizzling when power is applied (anode / cathode process using a battery charger). I have been working with super washing soda, white vinegar, and then finding that an electrified mild solution of muriatic acid has been the most effective - amazing actually, bringing 50 year old castings into what looks like a brand new part that just came out of the foundry! Makes Evaporust and other similar rust removers look like child's play.

So here's my problem. I have been experiencing corrosion just about literally after removing the parts from a good long soak in a baking soda solution that is supposed to neutralize the acids. I just can't seem to stop the instant flash rusting. When I say instant, I mean right in front of your face within 30 seconds. Spraying down immediately with WD40 does seem to help, but the castings still darken up, not looking like the brand new casting you see when you first pull the part out of the solutions (which is what I am after).

Has anybody here had experience with this? Can you tell me what I am missing? I know that cast iron castings are porous, and that the acidic solutions are soaking in deep, especially with electrolysis, which is exactly great for removing the 5 decades of corrosion, but I can't quite seem to nail down the "quenching" of the process. I need to nail down how to conclusively stop the reaction of being exposed to air once dried. I have researched this out on the ol' internet trying all kinds of methods. When I do seem to achieve some success, it comes at the cost of producing blackish magnetite across the castings. When you see what looks like a brand spanking new cylinder head come out of the electrolysis process, you are amazed, but then that all goes south just about right before your eyes. I have not yet tried what one ol' timer told me to do, which is to get some blocks of zinc and set up a quenching bath in a separate tub reversing the polarity of the electrolysis so that the zinc blocks become the sacrificial anodes to feed the castings. Again, sounds like it may work, and could even possibly result in yet an even better looking casting pickled in zinc.

Your experiences? Thoughts? Suggestions?

I have got it almost nailed down, but am apparently missing the last step to success. If I can get the castings to air dry and stay looking like the brand new castings they look like when first pulled out of the cleaning solutions, I will be over the moon (and can stop pulling my hair out in frustration).

Let me know please - thank you kindly!

[Ketzer]

I have zero knowledge about any of this, but reading through your comments you don't say how much humidity is in the area where you're running the experiments? May not even be a humidity problem, could just be the evaporative nature of coming out of the acids into regular air... thanks for sharing though! Interesting stuff!


Jeff-

[dhutton]

Flash rust is almost inevitable when you have super clean metal. A light media blasting should clean it up.

Or maybe a quick dip in evaporust.

Don

[jarhead]

Paul,
I have been using electrolysis for 10 years or so, started on old Ford tractors at first. I live in northern Colorado so i don't have to deal with much humidity.

After i pull the part out of the electrolysis tank i power wash it and then spray it with Klean strip concrete and metal prep. I don't know if there is a problem with automotive paint adhering, it works with tractor paint. I wipe it down with lacquer thinner before priming. The paint on my 42 Ford tractor never peeled or lifted. I'll find out on my Torino i guess

You can buy Klean Strip at big box stores, i get it at HomeDepot.

Joe

[dhutton]

Products that leave an acid or salt film should not be used with epoxy primers despite any manufacturer claims to the contrary imho.

Don

[TechNova]

WAG here but could you put some type of oil in your tank that would float on the surface? When you remove the part it would be automatically coated to prevent rust.

[jarhead]

Originally Posted by dhutton

Products that leave an acid or salt film should not be used with epoxy primers despite any manufacturer claims to the contrary imho.

Don

Thanks Don,

I've already sprayed some on the bare shell of my Torino, what do i use to clean it now?

sorry for any confusion i caused.

Thanks, Joe

[bretcopsey]

Originally Posted by jarhead

Paul,
I have been using electrolysis for 10 years or so, started on old Ford tractors at first. I live in northern Colorado so i don't have to deal with much humidity.

After i pull the part out of the electrolysis tank i power wash it and then spray it with Klean strip concrete and metal prep. I don't know if there is a problem with automotive paint adhering, it works with tractor paint. I wipe it down with lacquer thinner before priming. The paint on my 42 Ford tractor never peeled or lifted. I'll find out on my Torino i guess

You can buy Klean Strip at big box stores, i get it at HomeDepot.

Joe

I have had really good results with sheet metal using this product. I have parts that have been treated with this product and left otherwise bare for years barely showing surface rust. I’ve included some before/after pictures, smaller parts were left to soak. For larger pieces I found the key to be agitation with scuff pads or a wire brush while keeping it damp using a spray bottle. The bed of my 51 is still bare years later.

For me, hydrochloric aka muriatic acid was far too aggressive and I had the same flash rust problems you’re describing. I also had concerns after doing research and reading about the potential for cracking due hydrogen embrittlement. I would personally not feel comfortable experimenting with cylinder heads, blocks etc. that I planned to use without getting input from someone that truly understands the metallurgy.