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Thread: Anti-seize: copper or aluminum-based? Mixing OK?

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    Default Anti-seize: copper or aluminum-based? Mixing OK?

    There seem to be two (or more) types of anti-seize compound. A local shop used brownish (copper base?) anti-seize compound inside a BB30 BB. I added more AS at home to quiet it down. My anti-seize is silver (aluminum base?). Is there any concern of a reaction between the two metals in the compounds, along with the titanium bottom bracket?

    Thanks for any info.

    Thomas

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    Default Re: Anti-seize: copper or aluminum-based? Mixing OK?

    The answer is yes and no. An anti seize is composed of a lubricant plus metal flakes. The flakes are there principally to avoid dissimilar metal reactions between the two mating surfaces. The choice between copper and aluminum is determined by the metals involved in the mating, plus by temperature. Now realistically, for cycling, the choice of aluminum or copper is really irrelevant. Heat will never be an issue, and the anti seize function is still delivered by either metal for basically any metal ever encountered in cycling. If we had pure beryllium bikes mated with lithium bottom bracket shells, we might have an issue. But for ti, aluminum, and various steels, the type of flake isn't really all that important. Copper costs slightly more and is slightly more effective in preventing galling, which is a different phenomenon from dissimilar metal corrosion, which is why it's more commonly used in ti frames. In practice, this may be because the copper flakes are more durable and preserve some separation between the mating surfaces and allow that gap to contain some grease, which has nothing to do with chemical reactivity and is purely a mechanical matter. It's an issue that becomes relevant in high speed high temperature titanium applications such as aircraft engines, but not really in bikes. If you see both on the shelf, get the copper version. And I'd say that more because the aluminum seems to dry out a little faster, which leads us to the opposing issue in this discussion.

    The other part of anti seize is the grease base used. Now there are lots of different kinds of grease used in copper anti seize, driven by high temperature needs, speed issues, and so on. You're more likely to run into incompatibility in the greases used. They can be natural, synthetic, and all kinds of things in between. Just because they are greases doesn't mean that they will mix and live hospitably together. So practically speaking, it's the grease in the anti seize that creates the biggest issue. And thus my recommendation would be to clean one out completely before using the other. And I'd say the same thing with regard to replacing copper anti seize with more copper anti seize. Unless they came from the same can, clean one out before introducing the other one. One might have a very different grease base from the next.
    Lane DeCamp

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    Default Re: Anti-seize: copper or aluminum-based? Mixing OK?

    Quote Originally Posted by 11.4 View Post
    But for ti, aluminum, and various steels, the type of flake isn't really all that important.
    Hold the phone there, it can be of significant importance in certain situations.
    Copper flake is great for steel, but don't use it on stainless steels because you will get inter-crystaline corrosion, and the stainless will be likely to crack. At higher pressures and temperatures, ( that bikes aren't subject to as Lane mentioned) copper anti seize is not recommended on titanium as you will get embrittlement in your part.
    Aluminum flakes are great for stainless, but not so great on carbon and alloy steels (like chromoly) because you will get a cathode/anode reaction and your flakes will deteriorate and you will be left with less than zero protection in short order. This will happen even faster in a salt water environment.
    There are also plenty of blended metallic compounds, using combinations of aluminum, copper and graphite or moly and also non metallic ones as well using various combinations of graphite and moly. Permatex standard is a blend, and it fits a wide variety of applications.

    The grease bases are actually of less importance, as the idea behind anti seize is for the flakes to provide support after the grease has dried out. It's basically the solvent carrier in your chain lube.
    Eric Doswell, aka Edoz
    Summoner of Crickets
    http://edozbicycles.wordpress.com/
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    In Before the Lock

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    Default Re: Anti-seize: copper or aluminum-based? Mixing OK?

    And use gloves when you work with it. It is horribly sticky and gets everywhere.

    Great explanation above.

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    Default Re: Anti-seize: copper or aluminum-based? Mixing OK?

    Quote Originally Posted by edoz View Post
    Hold the phone there, it can be of significant importance in certain situations.
    Copper flake is great for steel, but don't use it on stainless steels because you will get inter-crystaline corrosion, and the stainless will be likely to crack. At higher pressures and temperatures, ( that bikes aren't subject to as Lane mentioned) copper anti seize is not recommended on titanium as you will get embrittlement in your part.
    Aluminum flakes are great for stainless, but not so great on carbon and alloy steels (like chromoly) because you will get a cathode/anode reaction and your flakes will deteriorate and you will be left with less than zero protection in short order. This will happen even faster in a salt water environment.
    There are also plenty of blended metallic compounds, using combinations of aluminum, copper and graphite or moly and also non metallic ones as well using various combinations of graphite and moly. Permatex standard is a blend, and it fits a wide variety of applications.

    The grease bases are actually of less importance, as the idea behind anti seize is for the flakes to provide support after the grease has dried out. It's basically the solvent carrier in your chain lube.
    Wait, are you saying that your basic silver anti-seize is counterproductive in an application with at least one chromoly steel element? I thought the whole point of the stuff was to block ionic transfer bonding.

    I just re-read, and I see that Permatex standard is a blend that works in a wide variety of applications. That clears up my confusion, I think.

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    Default Re: Anti-seize: copper or aluminum-based? Mixing OK?

    Quote Originally Posted by edoz View Post
    Hold the phone there, it can be of significant importance in certain situations.
    Copper flake is great for steel, but don't use it on stainless steels because you will get inter-crystaline corrosion, and the stainless will be likely to crack. At higher pressures and temperatures, ( that bikes aren't subject to as Lane mentioned) copper anti seize is not recommended on titanium as you will get embrittlement in your part.
    Aluminum flakes are great for stainless, but not so great on carbon and alloy steels (like chromoly) because you will get a cathode/anode reaction and your flakes will deteriorate and you will be left with less than zero protection in short order. This will happen even faster in a salt water environment.
    There are also plenty of blended metallic compounds, using combinations of aluminum, copper and graphite or moly and also non metallic ones as well using various combinations of graphite and moly. Permatex standard is a blend, and it fits a wide variety of applications.

    The grease bases are actually of less importance, as the idea behind anti seize is for the flakes to provide support after the grease has dried out. It's basically the solvent carrier in your chain lube.
    The grease bases actually are relatively important in a cycling setting. The areas where an anti seize is used are exposed to washout and desiccation, and one of the purposes of the grease is to bar moisture from creating an electrolytic environment. And for practical purposes, the grease is the lubricant up to around 350-500 degrees F, and the metal flakes actually decrease lubricity. At higher temperatures, the metal flakes soften and in effect plate the surfaces, but this doesn't happen in a bike. This is why some experienced mechanics basically use a basic grease for everything and dispense with anti seizes. As long as there is grease providing a barrier to water, it prevents electrolytic dissolution and the flakes of whatever is in the anti seize aren't needed.

    The effect in stainless deserves a couple comments. First, it typically only occurs at high heat, such as at a welded junction or in joints used in high-temperature applications. It's a big issue in nuclear reactors but not in bikes. Also, inter granular corrosion is a very shallow phenomenon, affecting the chromated skin that forms on stainless steel to prevent corrosion -- it goes only a few micrometers deep. It wouldn't crack your bottom bracket or even destroy threading.

    There are molybdenum disulfide anti seizes, as well as nickel ones, that have some additional benefits, but for cycling once more, there is no need. The industry has countless variants on the anti seize theme, but we don't really need to worry about them.

    The point about aluminum anti seize with copper also should be amplified. Some of the resins in carbon fiber can be very caustic to aluminum. BMC, for example, had some early carbon fiber frames with aluminum lugs. The frames were coated to prevent this very problem, but on small frames they had to shave the two head lugs to fit a short head tube, and thereby re-exposed the aluminum to the resin. The lugs basically corroded away in short order and BMC had to replace the bikes. However, pretty much anywhere you have a metal to carbon fiber contact on a frame is properly treated these days so this is no longer a problem. I've occasionally seen an issue if aluminum bolts are used with carbon fiber frames to mount water bottle cages, but only if the threading is part of the carbon (not a RivNut, for example) and if it hasn't been treated properly. Nearly everybody uses ti or stainless bolts now, so this isn't really an issue. But because you have aluminum seat posts, bottom bracket cups, headset cups, and so on, this is one reason why it does benefit to use copper anti seize on carbon frames since the copper can provide protection to the aluminum components.

    In all of this, two additional points. First, if the metal flakes are needed, they are going to be decomposing by being the victims of electrolytic corrosion in lieu of the frame or component. This means they don't last forever. Just because one uses anti seize doesn't mean the bike shouldn't be stripped, relubricated and reassembled on a regular schedule. It's also an issue that if the grease dries out, then corrosion will accelerate and/or the lubricative properties of the anti seize will become much less beneficial.

    Second, anti seizes used to contain a lot more metal flakes than they do now. Notice that there's probably no percentage of copper marked on your bottle of anti seize. The metal content has gone way down; molybdenum anti seizes have suffered even more. So you have less protection (and what you have is shorter lived) compared to a few years ago. Again, a reason for keeping to regular overhaul intervals. A lot of the anti seize you find out there is cheap (and the stuff made for the bike industry particularly so), which means you're really depending increasingly on the grease more than on the metal flakes.
    Lane DeCamp

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