Ekie
Active member
Steel will rust Matthew 6:19, however it can be delayed. The purpose of this thread is to discuss methods to remove or stop rust.
My back ground is in firearm assembly and finishing with 20 years experience. Specifically taking knocked down surplus post war military rifles (parts kits) and assembling on semi-auto receivers. Then either refinishing the entire rifle as new, or finishing the receiver to match the used and worn kit. This is the basis of my experience.
My education is in the fine arts and not chemistry. Any input from those with direct experience and or a formal chemistry education is very much encouraged to post feedback/correction/clarifications.
Here are a some examples of prior work:
IMBEL FAL receiver and surplus parts kit parkerized and painted with Brownell's Baking Lacquer.
TRW M14 parts on a Polytech receiver and parkerized.
SARCO surplus Italian 7.62 NATO M1 kit on a Beretta receiver - parkerized.
Recently purchased a 1995 Jeep Cherokee and found myself dealing with rust of this magnitude.
Methods of rust removal:
Phosphoric Acid:
Commonly used for the purpose of removing rust and to add a tart taste to carbonated beverages. Variously sold as the active ingredient in such products as Rustmort, Prep and Etch, Ospho, Navel Jelly, Metal Prep, and found in Coke a Cola, etc. Expect to pay about $30 a gallon for a 80% strength solution or about $16 a gallon for a 35% solution.
Phosphoric acid will remove rust and conversion finishes on steel, i.e. black oxide, bluing, and phosphates (AKA parkerizing). Will also remove paint, but it's not a very good paint remover. Have not seen it remove electroplating, i.e. zinc plating. Will take chrome off plastic.
Excessive exposure of steel to phosphoric acid will lead to heavy etching and will ruin the part/tool.
Because phosphoric acid can also leave a iron phosphate finish on steel I use it as the final rust treatment prior to finishing prep.
Heat greatly speeds up the process. Beware phosphoric acid can foam up while actively working especially when heated.
Phosphoric acid in a natural state is a white powder as such it is quite normal to have a white coating on your parts after treatment. The final finish can be applied over this white coating as it is quite durable. If you wish to remove this white chalky coating I have only found two methods that work. This can be important if you have some sort of industrial accident such as spilling the acid on your garage floor. Abrasion will obviously work. Better yet is a Chelation product such as Evapo-Rust. Will "melt" it right off.
Hydrochloric Acid:
This is the nuclear option and it is caustic nasty stuff. Since it is the same as stomach acid you can make fake vomit with it, kids love that type off stuff. Hydrochloric acid is why your dog can eat putrid stuff and not get sick. Available at the hardware store and Wal-Mart in a diluted form labeled muriatic acid for about $7 a gallon. Muriatic acid is commonly used to clean pools.
Hydrochloric acid in a approximately 10 percent solution is commonly used in metal prep in industry and has been connected to incidents of hydrogen embrittlement. Nice article on the subject:
http://www.bestbolt.com/white_papers/white_paper_05.pdf
In short it states that at least as far as fasteners go hydrogen embrittlement involves Grade 8 bolts that have been prepped with hydrochloric acid and electroplated.
Due to hydrochloric acid's caustic nature it is a paradox, will remove rust and will rust things. I now keep my supply outside after learning a lesson on the caustic nature of it's vapors emitted from a capped bottle. Because of this I only use it in extreme cases, that is on heavily rusted pitted furry scaled up nasty stuff. Used only as a early step and finishing up with other methods.
Is also a decent paint remover. Will also remove conversion finishes and zinc plating. However I have not been able to remove hard chrome with it. Will eat non ferrous metals for lunch. If you drop something in it and it starts to boil remove it immediately because your part/tool is dissolving before you eyes.
The real trick on using it is to stop the flash rust that develops as the parts dries after rinsing.
Electrolysis:
Considering this is the garage journal then this is about the cheapest method in that you should have the necessary equipment on hand. This involves hooking a car batter charger up to a sacrificial anode on the positive side and your rusty part on the negative with everything suspended in a electrolyte solution.
I find the process to be a bit to slow in that it's action is line of site (part/tool is flipped around and moved periodically) as opposed to acids that work in all areas of contact which is easy to achieve as long as total immersion is possible.
My setup uses a graphite rod as a sacrificial anode so that I don't end up with a bucket of gross red colored muddy slop.
Not sure how it does with paint removal or zinc plated parts, have not tried it. Did successfully remove rust from a parkerized shotgun barrel without damaging the finish. Not aware of any other method that can do that.
When you remove the part/tool after treatment you will find it coated with a black substance. Typically user tutorials call for removing this residue with abrasion which is not going to work on a heavily pitted part. Descriptions of this black coating have been describe as being various things but I am convinced that this black residue is magnetite. Phosphoric acid will dissolve this black residue in no time.
Don't think I will be using this process much anymore in that it is not as aggressive as hydrochloric acid and does not get all the rust off as well as phosphoric acid. And if I am going to remove the magnetite with a post treatment phosphoric acid bath anyhow then what is the point?
Chelation:
Sold as Evapo-Rust at your hardware store for $25 a gallon. Molasses can also be used (currently have no plans of going that route). Due to the high cost of Evapo-Rust I was slow to try this method.
Recently purchased some Rust911 and the math on it works out to about $4 a gallon. This could prove to be a economical choice depending on how long the solution will remain active.
On this forum there is a discussion on a home brew chelation solution utilizing ethylenediaminetetraacetate or EDTA:
http://www.garagejournal.com/forum/showthread.php?t=69793
Planning on posting progress on this method in this thread and once experience is gained I will update this section.
Abrasion:
Angle grinders set up with wire wheels, grinding wheels, sanding, tumblers, sand blasting, etc.
First mentioned downside, your part will get smaller.
Second downside regarding blasting is that the itty bitty media left laying around after use can lead to premature wear of parts later down the line. For example, sand in the engine bay of a vehicle later sucked up into the engine intake.
While I have a blast cabinet both in the garage and at work, and a "pot blaster" that can be used outdoors I rarely use them for rust removal in that in the majority of cases I find all other methods described here to be more effective in removing rust. However for large items where immersion is not possible like the frame on a vehicle my first step after a power wash is the wire wheel.
While I typically don't use abrasion for rust removal it is irreplaceable for prep work for getting a durable surface for you final finish to adhere to. For finish prep I use a vibrating tumbler for small parts and the blast cabinet for larger items. The end resulting frosted surface allows better bite for the finial finish to adhere to.
Vinegar:
Never tried it.
Citric Acid:
Another never tried it.
My back ground is in firearm assembly and finishing with 20 years experience. Specifically taking knocked down surplus post war military rifles (parts kits) and assembling on semi-auto receivers. Then either refinishing the entire rifle as new, or finishing the receiver to match the used and worn kit. This is the basis of my experience.
My education is in the fine arts and not chemistry. Any input from those with direct experience and or a formal chemistry education is very much encouraged to post feedback/correction/clarifications.
Here are a some examples of prior work:
IMBEL FAL receiver and surplus parts kit parkerized and painted with Brownell's Baking Lacquer.
TRW M14 parts on a Polytech receiver and parkerized.
SARCO surplus Italian 7.62 NATO M1 kit on a Beretta receiver - parkerized.
Recently purchased a 1995 Jeep Cherokee and found myself dealing with rust of this magnitude.
Methods of rust removal:
Phosphoric Acid:
Commonly used for the purpose of removing rust and to add a tart taste to carbonated beverages. Variously sold as the active ingredient in such products as Rustmort, Prep and Etch, Ospho, Navel Jelly, Metal Prep, and found in Coke a Cola, etc. Expect to pay about $30 a gallon for a 80% strength solution or about $16 a gallon for a 35% solution.
Phosphoric acid will remove rust and conversion finishes on steel, i.e. black oxide, bluing, and phosphates (AKA parkerizing). Will also remove paint, but it's not a very good paint remover. Have not seen it remove electroplating, i.e. zinc plating. Will take chrome off plastic.
Excessive exposure of steel to phosphoric acid will lead to heavy etching and will ruin the part/tool.
Because phosphoric acid can also leave a iron phosphate finish on steel I use it as the final rust treatment prior to finishing prep.
Heat greatly speeds up the process. Beware phosphoric acid can foam up while actively working especially when heated.
Phosphoric acid in a natural state is a white powder as such it is quite normal to have a white coating on your parts after treatment. The final finish can be applied over this white coating as it is quite durable. If you wish to remove this white chalky coating I have only found two methods that work. This can be important if you have some sort of industrial accident such as spilling the acid on your garage floor. Abrasion will obviously work. Better yet is a Chelation product such as Evapo-Rust. Will "melt" it right off.
Hydrochloric Acid:
This is the nuclear option and it is caustic nasty stuff. Since it is the same as stomach acid you can make fake vomit with it, kids love that type off stuff. Hydrochloric acid is why your dog can eat putrid stuff and not get sick. Available at the hardware store and Wal-Mart in a diluted form labeled muriatic acid for about $7 a gallon. Muriatic acid is commonly used to clean pools.
Hydrochloric acid in a approximately 10 percent solution is commonly used in metal prep in industry and has been connected to incidents of hydrogen embrittlement. Nice article on the subject:
http://www.bestbolt.com/white_papers/white_paper_05.pdf
In short it states that at least as far as fasteners go hydrogen embrittlement involves Grade 8 bolts that have been prepped with hydrochloric acid and electroplated.
Due to hydrochloric acid's caustic nature it is a paradox, will remove rust and will rust things. I now keep my supply outside after learning a lesson on the caustic nature of it's vapors emitted from a capped bottle. Because of this I only use it in extreme cases, that is on heavily rusted pitted furry scaled up nasty stuff. Used only as a early step and finishing up with other methods.
Is also a decent paint remover. Will also remove conversion finishes and zinc plating. However I have not been able to remove hard chrome with it. Will eat non ferrous metals for lunch. If you drop something in it and it starts to boil remove it immediately because your part/tool is dissolving before you eyes.
The real trick on using it is to stop the flash rust that develops as the parts dries after rinsing.
Electrolysis:
Considering this is the garage journal then this is about the cheapest method in that you should have the necessary equipment on hand. This involves hooking a car batter charger up to a sacrificial anode on the positive side and your rusty part on the negative with everything suspended in a electrolyte solution.
I find the process to be a bit to slow in that it's action is line of site (part/tool is flipped around and moved periodically) as opposed to acids that work in all areas of contact which is easy to achieve as long as total immersion is possible.
My setup uses a graphite rod as a sacrificial anode so that I don't end up with a bucket of gross red colored muddy slop.
Not sure how it does with paint removal or zinc plated parts, have not tried it. Did successfully remove rust from a parkerized shotgun barrel without damaging the finish. Not aware of any other method that can do that.
When you remove the part/tool after treatment you will find it coated with a black substance. Typically user tutorials call for removing this residue with abrasion which is not going to work on a heavily pitted part. Descriptions of this black coating have been describe as being various things but I am convinced that this black residue is magnetite. Phosphoric acid will dissolve this black residue in no time.
Don't think I will be using this process much anymore in that it is not as aggressive as hydrochloric acid and does not get all the rust off as well as phosphoric acid. And if I am going to remove the magnetite with a post treatment phosphoric acid bath anyhow then what is the point?
Chelation:
Sold as Evapo-Rust at your hardware store for $25 a gallon. Molasses can also be used (currently have no plans of going that route). Due to the high cost of Evapo-Rust I was slow to try this method.
Recently purchased some Rust911 and the math on it works out to about $4 a gallon. This could prove to be a economical choice depending on how long the solution will remain active.
On this forum there is a discussion on a home brew chelation solution utilizing ethylenediaminetetraacetate or EDTA:
http://www.garagejournal.com/forum/showthread.php?t=69793
Planning on posting progress on this method in this thread and once experience is gained I will update this section.
Abrasion:
Angle grinders set up with wire wheels, grinding wheels, sanding, tumblers, sand blasting, etc.
First mentioned downside, your part will get smaller.
Second downside regarding blasting is that the itty bitty media left laying around after use can lead to premature wear of parts later down the line. For example, sand in the engine bay of a vehicle later sucked up into the engine intake.
While I have a blast cabinet both in the garage and at work, and a "pot blaster" that can be used outdoors I rarely use them for rust removal in that in the majority of cases I find all other methods described here to be more effective in removing rust. However for large items where immersion is not possible like the frame on a vehicle my first step after a power wash is the wire wheel.
While I typically don't use abrasion for rust removal it is irreplaceable for prep work for getting a durable surface for you final finish to adhere to. For finish prep I use a vibrating tumbler for small parts and the blast cabinet for larger items. The end resulting frosted surface allows better bite for the finial finish to adhere to.
Vinegar:
Never tried it.
Citric Acid:
Another never tried it.
Last edited:
