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Hard Chrome

Discussion in 'Off Topic Threads' started by partygirl, Jan 13, 2009.

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  1. partygirl

    partygirl TS Member

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    What is "hard" chrome and will it rust?
     
  2. timb99

    timb99 Well-Known Member

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    Need more info, like what do you mean by hard chrome?

    Chromium is a metal, often used for plating over other metals, such as steel.

    Chromium will not "rust" in the common usage of the term, since the standard definition of rust is an oxide compound of iron (Fe2O3 if I recall correctly.)

    Chrome will oxidize too.
     
  3. partygirl

    partygirl TS Member

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    Colt has some semi-auto pistols with a hard chrome finish. I was wondering if they can be handled day to day and not start rusting like a blued finish, or do they need to wiped off after handling? I realize you cant leave them forever, but what maintenance is needed? I am not familiar with this finish.
     
  4. timb99

    timb99 Well-Known Member

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    Chromium plating is much more "forgiving" than blued steel.

    Blued steel is just steel with an oxide coating, kind a like rust, but a little different (Fe3O4 if I recall.)

    Think about it. The faucets in your house are probably chrome plated (now this is chrome plating over brass, but its still chrome plating.) Your faucets stay nice and shiny for a long, long time, even if you don't clean them regularly.

    I've never owned a chrome plated gun, but I'd still take good care of it, no different than a blued steel gun, but the chrome finish is pretty sturdy, and won't rust unless it is scratched down to the steel.
     
  5. timb99

    timb99 Well-Known Member

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    That is, the chrome plating won't rust, but the steel under it will rust if the chrome is scratched down to the steel.
     
  6. wolfram

    wolfram Well-Known Member

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    Hard chrome is an extremely durable finish. Very popular with 1911 shooters for the frames with blued steel slides. Near zero wear.

    Hard chrome won't rust or flake off under any conditions that you will expose a gun to unless you take it swimming in the ocean alot. Typical HC plating leaves a finish similar to brushed stainless in appearance. Good choice for a CCW piece finish.
     
  7. Baron23

    Baron23 Well-Known Member

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    "Hard chrome" vs "show chrome" or "decorative chrome" is due to the thickness of the electoplated layer of chrome (show chrome...bright shiny stuff like old style car bumpers) is very thin while hard chrome is layed on in thousands thickness. See below for details.
    ====================

    There are two different general applications for chrome plating: "hard chrome plating" (sometimes called 'engineering chrome plating') and "decorative chrome plating".

    Most people would not be very familiar with hard chrome plating. Hard chrome plating is chrome plating that has been applied as a fairly heavy coating (usually measured in thousandths of an inch) for wear resistance, lubricity, oil retention, and other 'wear' purposes. Some examples would be hydraulic cylinder rods, rollers, piston rings, mold surfaces, thread guides, gun bores, etc. 'Hard chrome' is not really harder than other chrome plating, it is called hard chromium because it is thick enough that a hardness measurement can be performed on it, whereas decorative chrome plating is only millionths of an inch thick and will break like an eggshell if a hardness test is conducted, so its hardness can't really be measured directly.

    Hard chrome plating is almost always applied to items that are made of steel, usually hardened steel. It is metallic in appearance but is not particularly reflective or decorative. Hard chrome plating is not a finish that you would want on a wheel or bumper.

    There are variations even within hard chrome plating, with some of the coatings optimized to be especially porous for oil retention, etc., others "thin dense chrome", and so on.

    Many shops who do hard chrome plating do no other kind of plating at all, because their business is designed to serve only engineered, wear-type, needs. If a shop says they do 'hard chrome only', they have no service that most consumers would be interested in. Follow the link for a list of some shops that offer hard chrome plating.

    Google is a wonderful tool :)
     
  8. Custer

    Custer Member

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    Baron23
    Interesting read! Is there any shops out there that can hard chrome the inside of shotgun barrels? I would like to chrome the inside of my perazzi barrels.
    Custer
     
  9. Baron23

    Baron23 Well-Known Member

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    Might want to talk to Metaloy (web site shown above). They do lots of gun work, don't know if they do the INSIDE of barrels or not.
     
  10. GunDr

    GunDr Well-Known Member

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    Chrome will also give you generally two color choices. Prepping the steel by giving it a high polish will have a shine and "color" like a car bumper. Whereas as a piece of steel bead-blasted first with leave the chrome with a much grayer color....some would color it "gun-metal gray".

    The stainless look referred to above, is actually a polished finish but the polishing is stopped before the buff/gloss look. You can see the very, very fine polish lines, just as you would in stainless steel.

    Doug
     
  11. Wolfman

    Wolfman Member

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    Right on Baron23. Actually, hard chrome can be applied to any thickness desired. We have tooling plated .0001 - .0002" thick - it's called a flash coat. Done a lot in the plastics and die casting mold trade for tool life - wears like a bear, and unlike TiN, doesn't require a lot of heat to apply.

    You are correct - Chrome does oxidize. However, like aluminum, the oxide coating is not gas permeable - it basically seals the surface preventing further oxidation. It's what makes stainless steel stainless. However, in salt water you will notice the SS fittings weeping rust. The reason is they are bedded into a compound, and O2 can't get in to seal the chrome.

    Flash plating bores is a great idea, and really helps prevent corrosion. All of my Win 101's are plated, and they are in great shape.
     
  12. X Trap 2

    X Trap 2 TS Member

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    I once bought a chrome plated 38 and it had a nice finger print embedded on the side that apparently was not wiped off and left there for years. Was still there when I sold it. Ray
     
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