;3013888]There's an encyclopedia to be written on rust removal and conversion, and there already exists two full volumes of disinformation on the process mislabeled "Electrolysis".
"Electrolysis" is really electroplating, and the only electrolytic action in the tank is ofr minimal water as occurs in any plating tank. We'll need at east a book on the difference between salt water caused rust and nonsalt containing rust.
Going to need a chapter on accumulating electrodes too, and minimally a chapter from guys who are sure carbon (Graphite) electrodes offer no advantage because they read on some site someplace where a guy hooked an elevator contact to his welder at 200 amps and it didn't derust the 4x8 sheet of steel any faster than the lawnmower blade he used in the B tank. Better add a chapter for the guys who insist on using Sodium Hydroxide and another for the high current group too. Most of the high voltage advocates died off forgetting to disconnect the tank before they reached in, so a page will cover them.
All I know is I can run my tank 24/7 at 24 volts 10 amps with graphite electrodes and filtration maintaining a clean clear electrolyte, and watch the rust walk off the object I'm cleaning.
It's a good method as long as the person doing it makes good connections and keeps grease & dirt out of the tank. It's a 2 step process in the case of salt water rust, possibly 3 to remove the salt first to prevent electrolyte contamination.
It will not maintain patina though, although that can be restored by allowing flash rust and polishing.
The process will work down to 31°f, and can be helped to heat itself by increasing current.
Chelation- is another whole volume unto itself. I do NOT encourage the use of overpriced miracle slop in a bucket sold at Horrible Freight or other vendors.
The process is well known and understood, and has probably been around for 100 years. Go to the nearby feed store, buy yourself a bag of cow molasses, and mix it up in a plastic bucket you can and should set outside away from your living area. The bucket will stink, it will grow mold, and it will attract flys and other creatures. The process is slow, and stops working below about 50°f. It is a very forgiving process unless you forget what you left in the tank for a month.
Molasses doesn't care if the rust is salt containing.
Months of scientific screwing around have demonstrated no gain by adding DC current to this process.
Vinegar & Muriatic acids will eat rust. They will also eat iron.
Neither belongs in any derusting process unless it is a high speed industrial process under constant monitoring.
If you have something you really want to screw up, use vinegar. What you pull out might look clean, but most iron that was there is gone and you have a hunk of carbon.
Phosphoric acid is both a remover and a converter, depending on the acid concentration. 4 - 8% by volume will convert rust to either a black or white phosphate coating depending on steel composition. Add some Magnesium to the solution and you get a slightly different coating simulating Parkerizing.
The nice thing about Phosphoric is it does NOT attack good steel. The second nice thing is the Iron Phosphate layer is bonded to the steel, and provides an excellent layer for paint & coating adhesion, eliminating the need to prime.
You can even tent and vaporize Phosphoric to treat oddly shaped objects.
The key to success with Phosphoric acid is complete wetting. That generally requires time with rust contacting acid.
There is a product line called POR based on marine phosphoric polymeric coatings that has developed a following. It is only a TEMPORARY coating, as is specified in the literature for use in marine environments. POR spends a lot on advertising, and people spend too much on POR products.
Oxcalic Acid works too, slow soak tank, and not really damaging to good steel. Just remember to rinse well.
Tannic acid is a converter, not as good as Phosphoric, but if you have tea sitting around, with lemon, NOT milk, why not try it.
Media blasting including water, will remove some of the rust you can see. It will also peen shut little rust gardens waiting for water and oxygen to grow and spall coatings off.
Soda blasting is not a process for removing rust. Soda is for removing "soft" deposits like tar and grease.
If money is no object in your consideration, red laser at high power will blow rust off surfaces.