Bought a 1939 Chevy 1.5 ton dual wheel 8 years ago from a friends dad in North Plat Nebraska in good body condition. Got side tracked with a new business in Victoria Texas near the coast. Now my project is being a...salted with rust and pits-pun intended. Got on the net and Stovebolt site and started looking for a lazy way to do the rust abatement and low and behold everyone has an opinion on the "best way" to remove all of the rust. Decided that science and experimenting trumps most of the methods that all of the back yard experts tout as the "best way to remove rust. I like blasting, Evaporust, sanding with a AD sander and just putting Ospho or Por-15 over the rust but I wanted to get to shiny new metal the lazy way.
Here are my science experiments that were tested and adjusted to prove out what actually works and it's upsides and downsides.. I call this the Good, The Bad, and The Ugly.
Tank no. 1 - Small parts up to 3 feet by 1 foot
Started using the evil diluted muriatic acid a.k.a. 30% HCL diluted with water or Hydroclhoric Acid in a 48 inch plastic tub.
Fast, takes all of the rust away and exposes bare metal in one to two days. Also softens paint. My paint is 80 year old DITZCO synthetic enamel from the July 1, 1940 Paint chip sheet called Boatswain Blue.
Does not remove paint unless allowed to soak for days. The longer you leave in the more likely you are to remove new metal but so far not a problem unless the part is already badly pitted and almost gone anyway. Does not effect good sheet metal based on 1 to 3 days of soaking. Also, does not leave the acid tank with anything except paint chips so tank stays clean a long long time.
Will flash rust in South Texas humidity in less than 5 minutes. Also removal of parts from the tank and rinsing must be done with extreme caution although I have actually removed parts from soaking with my bare hands. And yes it will burn your skin if you do not have your hose in you other hand to wash the acid off the skin. Starts to burn quickly if not rinsed right away. Now using tongs for safety! Daaah. Yes I even test its harmfullness!
Simple science states that if you dip a metal object in acid then rinsing with a base such as ZEP degreaser full strength then placing in a tub, which is Tank No.2, with some Arm and Hammer Washing soda, a.k.a. Sodium carbonate, not baking soda, neutralizes the hydrogen ions in the metal pores and I get a perfectly stable shiny new metal part to dry off and clean with no flash rusting at all.
Washing Soda has a Ph. of 11.5 to 12.5 depending on how much soda to water you use. Can be washed into the grass no problem. Muriatic acid is 4.5 Ph
Tank No. 3 - Large parts like doors, hoods and cowlings
Molasses in a 180 gallon cow tank mixed about 1 to 9 ratio of cattle molasses to water.
Molasses works as a a chelating compound that surrounds rust ( FeO2 and FeO3) molecules and lifts them off steel. It has some various mild acids including phosphoric acid that is used as a preservative but since Coca-Cola has a large amount of phosphoric acid in it I am under the impression only the chelating process is at work. This cleans every nook and crevice even the insides of the door locks to bring back to new shiny metal.
Works extremely well and makes your old doors and hood look like new, save and except the paint since it removes a lot of that as well but not all.
Cost of my molasses ran around $200.00 for 19 gallons, must be done in a area with a breeze or you get to smell "molasses sweet smell" for around 30 feet vicinity. Flies do visit more often but we have chickens so they are already here.
Takes roughly 3 weeks to do a fully badly corroded door with some sheet metal that was rotted but does clean the metal completely. Flash rusts in 5 minutes unless placed in tank no.2 with Arm and Hammer washing soda. Since I work a 24 hour a day job this was not a issue for me to take 3 weeks. Also, do not let the part "peek out" of the dark brown solution or you have rust again on the air exposed part.
Tank No.2 The washing soda and electrolyte tank. used to buffer the other 2 processes and clean small parts with electrolysis.
Neutralizes other dipping procedures and cleans the parts for painting. Hooking up my 41 amp DC power supply and running for 2 or 3 days makes the parts look shiny new with some black carbonate film.
Also does not require a neutralizing acid. Mild on the hands and can be washed in the yard. Part must be suspended with steel bailing wire and rotated to face the sacrificail annode as electrons move through the washing soda by line of site only.
Some assembly required and must be followed precisely or you could ruin a part. Not dangerous except must be done outside due to the H2O being split into pure oxygen on the cathode and pure hydrogen on the annode and utilizes the washing soda as an electrolyte to facilitate the rust removal process. Bubbles al ot so do not do this inside. Some like to use a grinder over the tank to hear the hydrogen pops when ignited..not kidding! Tank gets rusty brown foam on top and a settling fine particle of rust and impurities in the bottom and needs to be changed often like after each part.
After electrolysis is complete... it does not hurt good metal in any way shape or form, a fine black carbonate tint remains on the clean metal and must be wire brushed immediately before drying out or its semi permanent before you prime. Me, I am old, fat and lazy with little time to wire brush so into tank No.1 goes the part for a few minutes in the muriatic acid, cleans like new and must be neutralized by slipping part back into tank No.2 without the electrolysis to let the washing soda neutralize the reactive hydrogen from the acid tank. This black tint would not happen if you used Caustic soda but I am trying to reduce the danger to my grand kids in the yard until absolutely required. Not that muriatic acid is some lame tame product!
I have metal prepped all of the parts in the last few weeks after drying with a leaf blower by rinsing and scrubbing lightly over the parts with ZEP industrial degreaser soap, blow dry, hit with POR15 let dry and spray with REM self etching primer (contains phosphoric acid) then hang parts on a 3/4 inch PVC pipe in the garage to await epoxy primer and finish coats.
To finish out the running boards, fenders and entire cab I have purchased an above ground pool to make a large washing soda electrolysis tank. I will also mix in some lye a.k.a. caustic soda or Sodium hydroxide for these parts due to the large nature of each piece and the ability for lye to remove all of the old paint inside the cab. Will see how "jumbo parts" get rust and paint free. Supposed to heat the lye but I will just wait for it.
Now for the evironmental aspect of these "nasty chemicals".
I do not see any downside but I am sure I will hear some.
Tank No. 1 - Acid: I will use washing soda to neutralize Ph of acid to 5 or 6 Ph and dump in the garden and acidify my soil to help my blueberries and tomatos grow.
Tank No. 2 - Washing soda- will just pour out on grass no issue. After adding lye to tank no. 2 will pour some of the acid in tank 1 to neutralize the sodium hydroxide.
Tank No. 3 - Molasses will spread around the yard and in the garden to feed carbohydrates to bacteria and mychorizza fungi in my soil here. Could also pour in trail areas on deer lease to feed the deer as a lick!
Downside I have a Ph meter for gardening but will probably buy some Ph testing stripsas backup just to check....do not want to be mistaken on disposal.
Lastly, for your information, I am a locksmith with Certified Public Accounting background, not a scientist but I can read, a little. So the net has given me this information.
Also, as a fun fact the Ph scale was invented by a beer brewer to test his tanks of beer for Potential Hydrogen ions (Ph) after fermentation.
Sørensen (1868–1939), who held a PhD from the University of Copenhagen, Carlsberg Laboratory, a beer company of the same name, brewing being one of the oldest chemical industries.
I find it interesting that he died in 1939 as I attempt my first classic restoration of a 1939 Chevy.
The reason for this post was I spent enormous amounts of time reading forums from Stovebolt, Hotrods, Metal detecting, Texas A & M Conservatory, Electroplating and woodworking tool websites and found a lot of discussion about why and how and lots and lots of opinions but not much science so I made this my pet project to solve the old age problem of complete rust removal...the lazy way!.