What do you know about SCC and rifle barrels and associated cleaning products?

A friend who goes thru a lot of barrels (business and active competition) says that he had a target barrel go bad. That the throat is full of cracks. They have a bore scope and looked in there after the barrel had stopped shooting and also would not come clean of fouling. The barrel is from one of the very top makers and was kyro treated also. He said that this barrel maker has had about 50 go bad.

Maybe it's the steel or maybe something else?

Look at this link and tell me what you know.

www.corrosionsource.com/handbook/testing/scc.htm

It's basically the same thing as described on the referenced page, but heat is the big oxidizing accelerant in a rifle barrel. Hot nitric gas and too many degrees to remember.....all in a rush.

The steel fails along grain boundaries ond stress risers caused by rolling and machining. It looks like gator hide. That's what's known as a worn out barrel.

How about the ammonia used in bore cleaners. It's right there on the page!

If it is caused by ammonia he could simply charge his barrel with an opposite polarity. This should end the anodic corrosion.

Is this barrel CM or stainless?

Axel

Ammonia is not corrosive.

Axel- What in the world are you talking about? Charging the barrel with opposite polarity? Huh! If your talking about using an electrolytic cleaning system, it will have absolutely no effect on any ammonia containing solutions! Ammonia( NH3) in aqueous solutions is NH4OH. It is not corrosive and is most definately not an oxidizer. It's also not corrosive to either chrome moly or stainless steels. Some bore cleaners use ammonium sulfate ,however, again this is not an oxidizer, nor is it corrosive and it sure isn't effected by electrolytic cleaners. Barrels burn out because of alot of reasons, but the use of ammonia sure isn't one of them unless the basic laws of Physics and Chemistry have been changed.
Depending on the caliber, believe me it's possible to burn out a barrel in as few as 200 rds. If anyone doesn't believe this,just look through a borescope at extremely overbore cartridges such as a 30-378. This is why you don't see many 22-378's. You can see the erosion begin after 25 rds sometimes. Just imagine a big plasma torch because that's just what it is! -Rob

[ 09-16-2002, 08:55: Message edited by: Robgunbuilder ]

I've spent most of my life working in industry. Heat is almost always the catalyst in SCC as JBELK says. Caustic imbrittlement can be a factor as well as Nitric gases and Sulfur. Ammonia is a corrosive at high temperature. Ammonium Sulfate is not an oxidizer, but it decomposes at high temperature. The decomposition products will dissolve steel. Copper oxide is soluble in Ammonia; however, Copper metal must be oxidized before ammonia will dissolve it. The oxidizer in these solutions is most likely Ammonium Persulfate which is a strong oxidizer and will dissolve steel at a low ph.

If a person cleans his barrel with an oxidizing ammonia solution and didn't get the solution out before firing through the barrel, the hot acid gases from the gunpowder would change the ph of the barrel, and it could definitely be subject to SCC.

JD,

Do you think we are getting it out? If it were a plating tank there might be a triple rinse. When I used an ammonia containing bore cleaner I just wiped it once with a patch and oiled it. Does that get the ammonia out?

Don,

As you probably know Sweets 7.62 is made in Australia so we use it by the bucketful.

Our normal thing is to clean the barrel with Hopped and then dry that out. The a loose rag with Sweets up and down the bore nice and quick until it froths. Then dry out and then put Hoppes in. Then dry out Hoppes and put in oil or Hoppes again.

I have seen penty shooter leave the Sweets in there because they forgot and I have done it myself. Reports vary rom it does no harm to it might have done some harm.

My own feeling is that if it is left in the barrel it does create some roughness as the barrel fouls differently, more like a chrome moly and like a chrome moly it will sometimes shoot better when copper is left in it.

If you only dry Sweets out and then shoot that can increase pressure as the Sweets dries the barrel out.

Mike

Don--

One dry patch is NOT enough to get the ammonia out of the bore. Run several tight fitting patches through and then be SURE to apply a light coat of oil or a good oily solvent like Shooter's Choice or Hoppe's No. 9. I use ATF.

I don't EVER use ammonia based cleaners on my own barrels and only use them (Barnes CR-10) on badly fouled customer's barrels.

The anal retentive desire to have a spotless barrel is more an exercise in minutia than anything practical. There are a LOT of old over the course guns that have never been totally clean since the first round down range 50 years ago.

You'll find a barrel that's been shot and "cleaned" with a couple wet patches followed by a couple dry ones are MUCH more "consistantly accurate" and predictable than barrels labored over and constantly messed with using strong chemicals, ungents, potions and electric shock treatments.

I think 90% of todays cleaning supplies are more for the enrichment of the sellers than useful for the job they're sold for.

Buy a GOOD rod, a Boresnake for each caliber, a quart of Hoppes #9 and a bale of patches. That will handle 99% of the jobs you'll ever have for the next 50 years.

Don: Running one dry patch through will definitely not get the ammonia solution out. If you follow it with solvent or oil, you're taking care of the problem. If any oxidizing solution is left in the barrel, it will react with the oil and be neutralized. By the way I've used tens of thousands of pounds of ammonia with oxidizers for removal of copper scale in various types of process equipment. If a strong solution of ammonia and ammonium persulfate is allowed to dry on the floor, the friction caused by walking on it can set it on fire.

After reading these posts, I am amazed at the amount of misinformation presented. Let me try and set the record straight! Ammonia based cleaning solutions work not by oxidation but by complexation of Copper and copper ions. That's why the solutions turn blue/green(don't they)? Copper- ammonia complexes are colored because they absorb light in the visable region of the spectrum and copper salts are not! Thats inorganic chem 101! The purpose of the addition of weak( not strong) aqueous oxidizing materials such as peroxides and persulfates to cleaning solutions is to oxidize the most easily oxidizable metal i.e copper metal to copper ions which form the colored ammonia complexes slowly but strongly. Copper zero can be readily complexed with concentrated ammonia solutions, but this is dangerous to handle and expensive. For what it's worth, this is what I use in my very expensive benchrest .50 BMG rifle, where keeping the copper fouling down between strings is the difference between winning and losing a match! The disadvantage is that conc. ammonium hydroxide is dangerous to handle and you need to wear gloves and eye protection!!! In my view, the use of a proprietary mixture of Conc. Ammonium hydroxide and Liquid Ivory soap( my own brew- I call it Rob's bore shine) is the best bore cleaner I have ever seen! You can bet I'm not going to use something that will damage my $1000 barrel any faster than is absolutely necessary. I own a borescope and I look carefully. !
Now, the addition of weak aqueous oxidizers allows one to use more dilute and thus cheaper ammounts of ammonia in the solution. Unfortunately this process takes more time than the direct complexation approach I prefer, but is far less dangerous to the user. That is why some commercial bore cleaners use them. The blue/green complexes then can be swabbed out of the barrel and removed. The basis for this is that the oxidation potential of iron , Nickel and chromium are so much greater than that of copper that this procedure can be done with absolutely no risk of damaging the barrel. Assuming you don't leave the solution in for more than a few hours max( I think 20 minutes is more than enough time). Now were you to use a cleaner that contained chlorides, you would indeed damage the barrel by causing corrosion and in the past this is exactly what happened when well meaning folks made cleaning solutions with no understanding of the chemistry or metalurgy involved.
Now,if you leave these solutions in a barrel for a long period of time i.e overnight you run the risk of some slow/minor corrosion ( staining in reality) more likely caused by the dissolved oxygen in the solution than from the inorganic peroxides or persulfates present.
Thus, I personally never leave a barrel wet for more than 20 minutes and I clean the barrels with a dry patch followed by an acetone soaked patch( to remove all traces of Water from the bore). I always then swab the bore with a oiled patch ( a water removing oil) and shoot my next fouler from an oiled bore!
All my data suggests that the stress corrosion cracking seen in barrels is not caused by the cleaning solutions, but by the plasma torch effect of extremely hot burning gasses being expelled through a very narrow orifice at extremely high pressures. If you don't believe this just take a .22 barrel stub for example and attach a plasma torch to the stubb. Light -er off, then look at the stubb. It will look just like the throat of a 220 swift after 1000 rds. I hope this diatribe helps to put this issue in its proper perspective.-Rob

Gentlemen,

I am in agreement with what you are saying. I work in a chemical plant where we use tons of Ammonium Persulfate. And its like the man said this stuff is highly aggressive. It will eat through plain carbon steel in no time.

But I think Rob has the main point using reasonable sense about cleaning your weapons the issue is overbore cartridges and keeping the barrel from overheating. Hot, high velocity gas will cause errosion end of story.

Now, what is the experience with coatings to help with these errosion problems? In my work envrionment we have tried different coatings on high velocity control valves to help fight errosion. I wonder how the results are with rifle barrels?

Rob: In essence we agree. Ammonia is not the problem. The problem is the hot gases from shooting. The commercial solvents do need the oxidation of copper so that the ammonia-copper complex can form. Cu zero will not be complexed with weak ammonia without oxidizing it first. The ammonium persulfate in the solution is the oxidizer.

Ammonium persulfate is a very agressive oxidizer. If it is left in the barrel, and the the gun is fired it could react with the steel because of the heat. I have personally seen ammonium persulfate being mixed in a steel tank without the proper amount of ammonia ions present. The persulfate started eating the steel tank, and there was a lot of heat generated from the exothermic reaction. Addition of more ammonia stopped the reaction because the ph was raised.

I've heard of spraying carbarator cleaner down the bore. Anyone else ever heard of this?

Bear Claw---

Of course I've heard of people squirting carb cleaner down a barrel.......

My question is -- How did you manage to get a gummy deposit of engine oil, gasoline impurities, dust, and varnish IN the barrel to begin with?

This is what carb cleaners are designed to dissolve. I see nothing there that equates to what might be in a barrel so it makes as much sense as swabbing it down with hand lotion!!

Rob,

You use the soap and ammonium hydroxide too? I thought I was the only one to do that ! Works great. Never bothered with the acetone, I just follow with Ed's. I used the original formula with the exception of synthetic ATF (more detergents) and I used the turpentine (smells better) plus about 200 grams of lanolin. The lanolin really does a good job of coating. When I go shooting I use Lectroclean (1,1,1-trichloroethylene) to wash out the bore.

First let me say no disrepect to anyone intended! This is an area I've spent alot of time on and I'm a trained Chemist by profession to boot!
JD- I think your talking about making ammonium persufate from persulfuric acid and ammonium hyroxide. Yes of course this will be exothermic! Yes , hot persulfuric acid will indeed corrode steel ( probably glass also) however when it's being neutralized with ammonia this reaction ceases This is precisely my point. Ammonium persulfate is still a very weak oxidizer in the grand scheme of things. I can assure you that perchlorates and even nitrates rank far above persulfates in this regard. Even if one were to leave pure ammonium persulfate in a rifle bore, I honestly doubt it would corrode the steel by itself. Any corrosion that occurs would in my opinion be more like due to the fact that ammonium persulfate is highly hydroscopic and will attract huge amounts of water into the bore which would in itself account for any corrosion that occured. A good swabing with a dry patch and oil would resolve this concern.
Infact, dilute ammonia solutions do react with copper zero albeit more slowly than a concentrated solution. You just have to wait longer for the blue/green complexes to appear.
The conc. Ammonium Hyroxide/Ivory soap ( and some other stuff) really works better than carb cleaner/ Butches bore shine , 7.62 and sweets. The only problem is it's dangerous to use!
I only use it because it works and I'm ver very carefull in how I handle it!
Rodger- synthetic ATF is a great product to leave the bore coated with between range sessions! Kroil is amost as good.
Bottom line continues to be SCC is caused by the plasma torch effect of the hot gasses produced particularily in overbore cartridges. I might add that all barrel steel is not the same and some are far more easily plasma torched than others. This is another story!-Rob

Rob: I am also a degreed chemist. I've spent over 25 years in: research and development, field services, sales and service of chemical cleaning formulations. What I'm speaking of is actual hands on experience.

The steel tank that was being dissolved was when technicians were mixing a solution of ammonium persulfate and ammonium hydroxide to dissolve copper out of a utility boiler. The reaction of the persulfate and iron is very agressive and becomes uncontrollable if the ph is not high enough.

Gents,

I think that I'm missing something here, namely the "Stress" part of "stress corrosion cracking"? Aren't we really discussing chemical corrosion from use of solvents, and erosion due to combustion? Chemical intergranular corrosion due to cleaning solvents?

The main major stress that a rifle barrel sees is during firing, and that is only for a very short duration. There will also be residual stresses in the barrel due to manufacture/machining, and stress in the barrel threads due to torque. I doubt that much corrosion forms during that instant that the barrel is under stress during firing.

In the aerospace industry, we sometimes test parts/materials for susceptibility to SCC. We do this by applying a tensile load to the part (usually around 70 percent of the ultimate tensile strength of the material) while placing it in a corrosive environment (salt spray) for a set period of time (X days). This does not seem to me to be a description of what happens to a rifle barrel.

What am I missing here?

Regards, Bill

Dang, Jack.

You mean all that hand lotion over the years was wasted?

Bill: SCC can be caused by chloride which is what causes the cracking during the salt spray test; this is being tested using tensile stress. Cracking can also be caused by other chemicals due to heat and or pressure stress. Caustic cracking, especially of Stainless Steels is caused by a high concentration of hydroxide ions at high temperature/pressure. You can also have cracking due to sulfide ion at high temperatures/pressures. When a rifle is fired several times in succession, you definitely have the potential for SCC because of the high temperature and pressures produced. If the right chemical is also present, SCC is definitely a possibility. Maybe there's a metallurgist around who can explain it better.

Thanks for the explanation JD. Sounds like we have a vast combination of contributing factors....

I just always thought of SC as corrosion occurring as a result of applied stress (under certain atmospheric conditions). The stress causes the grains to "stretch", and the chemical environment causes corrosion at the boundaries, weakening the material. Conversely, you can have chemically caused corrosion that induces stress in the material and contributes to material failure. Kind of which caused what - did the stress cause the corrosion (SCC) or the corrosion cause the stress?

Regards, Bill