Chrome plating gun barrels


January 10, 2010, 04:05 PM
I have a chrome plating guy whom I have been sending work to for a few months now ( mostly random furniture parts, knobs, fittings etc. ) and I want him to plate an old revolver of mine. He says that he will not plate gun barrels and refers to some "hydrogen ion" or something ( I forgot exactly what it was) that would make the inside of the barrel unsafe. I'm pretty sure he doesnt know that much about guns - but I am no expert either. I tried to tell him that chrome plating (specifically the insides of barrels) has been going on for years. Do any of you know what my plating guy is talking about? I think the gun could be plated just fine. NEF .22LR R92 Ultra. Please help me to convince him to chrome it.

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January 10, 2010, 04:17 PM
It is called Hydrogen Embrittlement, and your plater is quite correct to refuse to plate high-stress parts like gun barrels or frames.

Hydrogen Embrittlement was first discovered in the aircraft industry before or during WWII.

The plating process drives excess hydrogen ions into the steel, and sets up internal stresses.

There were reports of aircraft landing gear legs breaking off while the plane was parked on the runway.
And new parts exploding in the parts bins at aircraft factories.

Better listen to him, as he knows what he is talking about.
He knows enough to not chrome plate guns without the necessary means to remove the excess hydrogen from the steel anyway.

And he would also need a Federal Firearms License to do it legally, if he was to do it.

chrome plating (specifically the insides of barrels) has been going on for years.Again, there are methods & equipment to do it safely on guns and aircraft parts.
But your bumper shop guy doesn't have the equipment.


January 10, 2010, 10:42 PM
+++++1 rcmodel Hard chrome and decorative chrome are very different things.

Alpacca 45
January 14, 2010, 01:39 PM
Guns with hard chromed bores are designed to take the thickness of the chrome, they also have specially designed rounded rifling,

With conventional rifling, the chrome would all plate on the sharp top corners of the rifling lands, with precious little on the middles of the lands and grooves, and almost none at all on the bottom corners of the grooves.

In short, with a bore that wasn't designed for chrome, at best it won't plate evenly, at worst, you'll make it dangerously tight

The guys are right about hydrogen embrittlement from hard chroming.

For critical strength parts, there are specifications for how long the part should be held at a certain temperature, to give the hydrogen time to diffuse out. From memory I think it is something like 48 hours at 200C. you'd need to check if you were to do it, and Do not go to 250c as that is where temper brittleness starts in many steels.

Jim Watson
January 14, 2010, 01:54 PM
Once upon a time, the old Marker Machine Co. would chrome plate a bore aftermarket.
Col Charles Askins plugged them frequently.
But that was so long ago that they are not even mentioned on the internet.

My gunsmith is a real worrier over hydrogen embrittlement of plated pieces. A deputy's blown up satin nickel Combat Commander was just another nail in the coffin. I wonder about the commercial reload training ammo the county had bought, though.

Ed Harris once described reworking a .223 barrel that had been factory chrome plated over reamer marks and copper fouled terribly. He said that by the time the plating was stripped and the steel lapped smooth, he had a .225" barrel. He said it shot well with flatbase bullets that would slug up a bit to fill the grooves.

navyretired 1
January 20, 2010, 04:07 AM
I can't say for guns but when I had some model T springs chrome plated to get rid of hydrogen embrittlement I heat soaked springs in oven at 400 degrees F. for I think 4 hours (if I remember right) If not done springs will break as soon as stressed.
I did this on recommendation of plater and I still have those springs 20 years later.

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