Hot Salt Bluing Setup Questions/Input

Hey guys, I ordered some steel in today to start in on making bluing tanks since I have access to a plasma cutting table and nice TIG welders. My tanks will be 40" long x 6"wide x 9" depth. I will be also making the stands but I need input on how to work the burner setup.

I will be heating 3 tanks out of the 5 total. 1 degreasing tank, 2 salt tank, and 3 boil out. arranged in a "U". on my right I will have a boil tank with dicro 909 and a fresh water rinse. infront of me the hot salt tank. to the left a fresh water rinse and a fresh water boil out tank.

What do you guys suggest or have found for burners, burner hole size/configurations and LP regulators, pipe diameter. I will make my own burners as of right now unless you have found a product that is easier vs producing them. I would like to have valves at each tank as well as a master right before the 3 way split. Looking for a efficient setup as well as something that will pass the test of time. My plan is to pipe into a 100lbs propane cylinder. Is this big enough to last me a few runs or do I need to go up to something like a 200lbs. don't want to be refilling it every time I turn around.

Any input or help will be greatly helpful

USNRigger

Aren't you the one who is in Trinidad? If so, go up to the college and ask the instructors in the gunsmithing program. I am sure they would be happy to discuss this with you.

Ive used those tanks many times and know the setup. I also know that setup could have been there for sometime. School started 1947. I wanted to look at modern or other approaches or ways before I start in on the stands and burner setups. I will be talking to them as well but classes have not started yet and the instructors are in and out.

I use the Brownells setup for hot bluing. I have 5 tanks. They are in a U shape. My first tank is 909 cleaning at 185°. The next tank is cold water that has to overflow to stay clean. The next tank is the bluing tank at 290°. The next tank is back to the cold water. The next tank is hot boiling water. The next tank is water displacing oil.
The burner for the bluing is larger than the other 2. I use 1" black pipe from a 100lb. tank. So far I have got 3 cycles on this tank. I ran the 1" pipe to a tee and one half continued the 1" to the bluing tank. The other half was reduced to 3/4" for the other 2 burners.
If you buy a 100lb tank buy a spare. You don't want to run out in the middle of a job. What bluing salts are you using?

Intended on running No. 7 as its what we used at school and its time tested and ive seen the results. I will also be making 1 Stainless tank for both park'ing as well as being able to buy some No. 84 down the road for stainless black/blue.

So you are running 1" round and 3/4 round plumbing? What is your burner setup? round with .060" holes? I will be building almost a exact clone to your tank setup. what regulator are you using?

The burners came from Brownells. I will have to check the hole size. They come with different orifice sizes for LP or city gas. The regulator and tank I bought at Lowes. I should have bought the extra regulator that shows how much is in the tank.
There are many items you will need for rebluing that are not in any kit. Such as a piece of heavy steel to stir the salts and to break it up when cold. Don't EVER put heat to your salt tank without breaking up the salt. Adding water to the salt tank while running is a pain. I add water with a stainless ladel from the hot water tank. Mark all of your tanks so you know when you have to add water. Make sure the water you use is filtered. I use a household type with a sand and charcoal filter.
On your cold water tank you have to have an overflow. I put an inlet at the bottom of the tank with a bulkhead fitting.
I can send you some of my info that I got from Brownells. It really helps. If you have any questions, p.m. me.

Thanks for the input. I have the brownells printed bluing instructions, and I made my hose attachment for adding water, and my scraping paddle for breading up salts ext. Hmm never figured on filtered water. I don't think we ever filtered outs up on campus, in fact I know we don't.

let me know what you find on the orifice holes for LP

It depends on your water. If you have well water with a lot of minerals, you have to filter it. A filter doesn't cost much and it will prevent many problems.

At the USAF gunsmith shop, we used capped steel pipe with holes drilled in them as gas burners to heat the steel tanks. Pipes were the ame length as the tanks. We completely dispensed with using silicated cleaners prior to bluing altogether. Instead, we wiped everything down with MEK (outdoors), then straight into the bluing tank. Very few components needed to be re-blued after we started doing that. After bluing and rinsing, everything went into an oil tank, both the bluing chemicals and the post-treatment oil came from Brownells. We had an assortment of perforated SS baskets to contain small parts. Close temperature control of the bluing solution is very important.

Another important thing you need to make is adjustable brackets for the mounting of the pipe heaters. You need just the tip of the flame to touch the tanks.
I have the orifice sizes for the heaters. For natural gas use #32 drill for the bluing tank and #43 drill for the hot water and 909 tank. For LP gas use #51 drill for the bluing tank and #53 drill for the hot water and 909 tank. If you have the Brownells instructions it lists all you need to set up your heaters. Just make sure to make the heaters out of black iron.

This is from the manual I developed regarding bluing of the M9 pistol at the USAF gunsmith shop. These were for USAF General Officers.
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3. Bluing

Bluing (i.e., hot bluing) is a chemical process for achieving an attractive finish on steel gun parts. It is essentially a controlled rusting process in which a very thin layer of black iron oxide (Magnetite, Fe3O4) is chemically formed on a steel surface. While bluing alone provides a small degree of protection against abrasion and corrosion, its principal function is cosmetic. Hot bluing cannot be used on non-ferrous metals such as aluminum or brass, or on stainless steel. In fact, the chemical bluing bath will attack and destroy aluminum. If it is necessary to impart a blue-black finish to such metals, other methods must be used.
Even though a blued finish can be applied to any clean steel surface, its final appearance will be no better than the surface finish of the bare metal. If a bead-blasted steel surface is cleaned and blued, the blued surface will have the same dull frosted or satin appearance as that of the bare metal. If done well, this finish is not necessarily unattractive, and some gun manufacturers produce such finishes on their guns because bead blasting is much faster and less costly than hand polishing. However, the highest-grade gun finish is a bright deep blue, which requires a mirror-like surface finish on the base metal.

a. Parts cleaning- It is impossible to obtain a uniform blue finish unless the steel parts to be blued are free from corrosion, dirt, and grease. Therefore, cleaning polished parts thoroughly prior to bluing is essential to the success of the entire finishing process. In the gunsmith shop, considerable time often elapses between the completion of the surface preparation of the parts and the bluing process. The polished parts are therefore submerged in containers of cleaning solvent to prevent surface corrosion prior to bluing. It has also been discovered that the parts cleaning solvent itself does not do a complete job of removing grease and wax from the metal surface deposited by the polishing operation. Immediately prior to bluing, the parts to be blued are removed from the cleaning solvent bath, thoroughly wiped with paper towels, blown off with an air gun, then wiped carefully using paper towels and methyl ethyl ketone (MEK). The procedure used is to spray parts with MEK using a plastic spray bottle, followed by wiping them with a paper towel. Care must be used when MEK is used, because it is very flammable and contact with skin can cause dermatitis (removal of body fats from the skin) in some individuals. MEK must always be used outdoors or in a well-ventilated area, no smoking or open flames can be allowed close to the workspace, and operators should use proper personal protective equipment, especially polyethylene or rubber gloves. Use of gloves also prevents contamination of gun parts by body oils through skin contact during handling.
b. Bluing- The bluing process requires proper safety procedures to be followed. Solutions used are very hot, and the bluing chemical is caustic and can cause blindness if allowed to contact the eye. Therefore, the use of rubber aprons, boots, gloves, and eye protection is mandatory.
The bluing process begins by thoroughly cleaning the parts to be blued, as previously described. The earlier procedure was to immerse them in a boiling detergent (similar to that used in automatic dishwashers) bath while suspended from rods on fine steel wire, followed by rinsing in a hot water bath, and then into the hot bluing chemical bath. More recently, since MEK wiping has begun (as previously discussed), it has been determined that immersion in a hot detergent bath is unnecessary prior to hot bluing. After cleaning, smaller parts are placed in baskets rather than being individually suspended. Some parts may be placed together on rods (such as hammers and triggers), while slides are mounted on a special fixture, or rack.
A commercial hot bluing chemical is used, Oxynate 7, from Brownell’s, Montezuma IA. The chemical is dissolved in water for use, according to product instructions. For use, it is very important to maintain the bluing chemical bath at the proper and constant boiling temperature (290 – 295 degrees F.). This is done by adding water as necessary to replace water boiled off. If the temperature of the bath will not reach the desired boiling temperature range when the proper liquid level in the tank is maintained, then additional Oxynate 7 should be added. The parts, which are either racked or in baskets, are then immersed in the bluing chemical bath, visually inspected periodically during the bluing process, and removed when bluing appears to be complete. The residence time of parts in the hot bluing tank will typically be about 30 minutes.
c. Post-bluing – When bluing is determined to be satisfactory, the parts are removed from the bluing tank and immersed in a cool water rinse bath directly below the bluing tank. They are then inspected once more (preferably in daylight) to determine that no further immersion in the bluing tank is necessary. If the blued finish is satisfactory, the parts are then immersed in a hot water bath (to dissolve any residual bluing salts) followed by immersion in a hot water displacing oil bath (also a Brownell’s product) which prevents further corrosion by any remaining bluing chemicals. Upon removal of the parts from the oil bath, followed by draining, the bluing process is essentially complete.

I have been bluing for quite some time and here is what I have to say...

First off, not to discount instructors wisdom but someone suggested you get the info you need from teachers...there is a big difference between instructing and doing it as a business.
Second, I have rather hard water and do not use filters, never had a problem. Hard water is alkaline...so is the main active ingredient chemical {sodium hydroxide} you will be using. On the off chance that your water is slightly acidic {very extremely doubtful unless you have to bail it out of a farm pond} the base {sodium hydroxide} is so alkaline it wont matter.
Third, and this is the main one...beg, borrow, steal or whatever it takes to buy electric heat elements as a heat source. I get that propane is cheaper to start with, but I suggest you visit a gunsmith that has been using propane burners to heat with for some time. You will see a lot of corrosion and the constant battle to keep all those little holes clean enough to get a good even heat on the tanks. That is time you could better use polishing other parts to blue. You cannot charge for maintenance of your equipment...that is overhead. What you wont see there, but you will very quickly when you start doing it, is how tedious and what a pain it is to keep the temperature at the correct level with propane. If the temp goes over by not too much the parts turn red and you lose your tail having to polish all over again for free. In the not too distant future when you have to redo all the rusted and busted nasty black iron pipe burners you will quickly realize that you should have went with electric to start with.
Omit the water soluble oil...it is simply not needed. You will probably use it to start with, like all of us did, because somebody says you need it...you will figure out later that you don't and that it is just an added expense and delete this step {like all of us that are making money did.}
Best of luck in your new endeavor.

Edit: Oops, almost forgot...spare no expense at adequate ventilation if you are doing this inside of a building...the chemical is so corrosive that if you do not ventilate properly you will not believe the mess th efumes can make inside even a large enclosed area.

I don't think you will be able to find the electric heaters for the bluing tank. The people that made them for Brownells and others stopped making them. They could not keep them water tight against the corosion and heat. When Brownells last sold them they were $1500 just for the heater! Then you needed the thermostat and controls to run it. You just can't throw any heater and thermostat into this stuff.
If anyone knows were they can find electric heaters that will work in this stuff please let me know. But I will bet you will spend well over $2000 for one! Now an electric heater will work on the hot water tank and the 909 tank but I don't know who sells them.

Yes, proper ventilation will be used. I know how that stuff gets, no fun and very corrosive. I will be going with propane, its just easier and like said i dont know or how much a electric element that big would be.

I will be going up in the morning to talk with the guys about heating setup and see what they think as well as take a better look the schools setup. Mainly the burners.

There are strip heaters that can be mounted on the outside of the tank bottom. Tig weld studs to mount them.

can they get a tank 40x6x9 tank up to 290 degrees even in colder weather?

Probably take 6000 watts or more to do that.
These type of heaters get mounted tightly to the tank.
I'm sure they are still available but don't remember what they are called. They are used in industrial applications. I don't remember them being super expensive. You might find some on E-bay.

There are obviously differences of opinion on the best tank heating methods. However, it would be difficult to beat the simplicity and economy of gas. We had no problems whatsoever with the gas burners, either in getting plugged holes in the pipe (that never happened in my experience) or in temperature control. Our burners were fired by natural gas, not propane tanks. I have some pictures of the USAF bluing tank setup, including the burners somewhere and may post them if I can find them. The burner pipes, as I remember them, were simply steel gas pipes, and the holes were drilled fairly close together, perhaps an inch or less apart. I don't remember the hole size, but fairly small, maybe 1/8" or less. It produced essentially a linear flame the length of the burner and tank. No special controls, just a valve on the gas line. We had a thermocouple in the tank and a temperature readout meter some distance away, never had a problem in keeping the temperature spot on where it should be. That bluing setup had been used since the 1980s. The tanks were inside a diked area (in case the tank sprang a leak), and covered with a vent hood with blower to exhaust to the outside. It was located in a room separate from the rest of the shop. We just used normal tap water for everything, and the local (San Antonio) water supply is fairly hard. Regarding the final oil tank, we used it mainly because it had always been there. It was a two-tank setup with the top tank being heated water, and the lower tank being the oil solution. Parts went from the bluing tank to an unheated rinse tank, to the heated water rinse tank, then to the oil tank.

Thinking of doing the same thing. Keep getting hung up on getting gas into the burners. Anybody done this with out using a pre made orifice before the pipe burner?

You need an orifice before the burners and an air inlet like on a gas grill that is adjustable for the proper flame. The orifice has to be the proper size for the gas you are using. You can't just pipe gas into the burners without an orifice. I suppose you can make your own orifice by drilling the proper size hole in a pipe plug but you still need to put an air inlet with an adjustable door near the orifice.