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OT - Corrosion caused by grease

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  • Evan
    replied
    Should chrome plate very nicely.

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  • darryl
    replied
    Or polish them up with carnuba wax.

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  • wierdscience
    replied
    What about PTFE pipe sealant? Or a thin wipe of silicone gasket glue?

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  • Rich Carlstedt
    replied
    Ian
    I am somewhat familiar with Rupture disc's
    we used them in Plastic extruders, only at 6,000 to 12,000 PSI.
    First of all, you are working with Nickel, one of the best corrosion proof
    metals around. I suspect that either you are not getting Nickel discs, or
    the disc's have a flux product residue. or you are getting spikes in the pressure line, or you are running too close to failure during operations
    So
    Can you confirm the base metal and is it an import?
    Have you washed the disc's before using them? or litmus test them
    I have seen salt spray tests on Nickel and it sure seems your experience
    is exceptional. If you want to protect the disk coat it with paraffin wax.
    What confirms that the pressure is OK, We had the problem with several customers, and it was the pressure gages that were off. (ie. the disc's worked)
    Lastly, does the failure occur at the same time of day ? or point of operation?
    ( customer had an operator close off the recording gauge , and increase pressure to get more outpoint )

    hope i have given you food for thought.
    Rich

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  • Mcostello
    replied
    How do you get it out of Pam Andersons front bumpers IS the question I like to see answered.

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  • J Tiers
    replied
    or even plain old vaseline?

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  • ttok
    replied
    Paint?

    How about coating the outside of the frangible disk with paint? A.T.

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  • pcarpenter
    replied
    Here we go again.....Give Evan a break Millman. I knew just what he was talking about when he mentioned it, from a previous post that I am sure you would have given him crap about too. It is used as fuser oil and most folks could come up with a bit if it was useful...maybe a lot more as the stuff is used in lots of laser printers and copiers as a consumable. The amount left in an empty bottle would go a long way.

    Thanks to a post from Evan about the same material before, I was able to get some and put it to a very good use on the plastic sheave bushings in the VS head on my Bridgeport. There are plastic bushings glued in place that slide up and down both on the motor shaft and the spindle end. Petroleum is questionable on plastic and you don't want to use anything that will sling off and get on the belt. polyhexawhatyoumacallit is ideal. Get any on anything and wipe it off and it will be really slick for a really long time. A thin film works wonders and it is OK on plastic.

    Paul

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  • J Tiers
    replied
    Originally posted by Magic9r
    Grease is a suspension of oil in a soap base, your results don't seem that surprising.
    Ah, but there are greases, and then there are greases. They differ in the "soap base", among other things.

    And the term "soap" refers to a classification of compound. We are not talking about "Dial" here....

    The soap may be any of several types. The types vary in temperature response (melting point), in resistance to water, and other properties. A part slushed in a water resistant grease (if it doesn't react with the grease composition) should stay good for a considerable time if it doesn't get hot enough for the grease to run off.

    But, I don't know how resistant a lithium grease is. It would presumably be a lithium soap base, and whatever the properties of that base are, that's what you would have.

    The lithium types are made for a particular purpose, and I don't think slushing parts is one of them.

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  • Evan
    replied
    I have a couple of jugs of it in my shop, if you will pardon the expression.

    You can buy a product at any auto parts store called Rain-X for coating windshields so the rain beads up and runs off. It's polydimethylsiloxane.

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  • Guest's Avatar
    Guest replied
    Sure

    {{polydimethylsiloxane.}} Having 500 lbs. of that stuff in my tool boxes was required by most companies I worked for. They would come out on a regular basis and check your boxes. You could be fired for having less than 476 lbs. in your posession. Evan, what were you thinking????

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  • Evan
    replied
    I would try coating with polydimethylsiloxane. It's an inert silicone oil used in among other things, Pamela Anderson's front bumpers. Once something is coated with that stuff it is almost impossible to remove and leaves a permanent layer. It should make no difference to the rupture properties and doesn't react with much of anything. You may have some around in the form of fuser oil in a cleaning wick assembly for a laser printer.

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  • nheng
    replied
    Instead of a grease based approach, how about conformal coating the disks prior to installation (similar to what's used to seal printed circuit boards in harsh environments), or perhaps specifying them with a thin laminate of (appropriate) plastic on one or both sides. Either of these should have minimal effect on the rupture characteristics, but of course would need to be tested. Den

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  • Ian B
    replied
    Thanks for the suggestions guys; today, we installed 3 disks with different protective coatings;

    - Silicone grease
    - Copper based antiseize
    - Nickel based antiseize

    I'll let you know how they stand up...

    Ian

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  • Magic9r
    replied
    Grease is a suspension of oil in a soap base, your results don't seem that surprising.
    Try a thin coating of molten wax instead of grease.
    How about silicone grease? I don't think theyhave the same composition as petroleum greases,
    Or maybe about a brush painted etch primer followed by brushed 2-pack epoxy paint?
    Can you get a non-metallic rupture disk for your application? I know some are available in a ceramic for some pressure ranges.
    Good Luck,
    Nick

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