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galvanic reaction

Discussion in 'Security Alarms' started by Dr. Phil, Mar 31, 2005.

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  1. Dr. Phil

    Dr. Phil Guest

    Why do manufacturers give us resistors that are made of a different
    metal than the copper wire we are using? High voltage electricians know
    that you can't connect an aluminum and copper wire directly to each
    other. Roofers know you can't nail copper flashing with aluminum nails.
    Simple moisture in the air can cause galvanic reaction between the
    copper wire and whatever the resistors are made out of [looks like
    aluminum] causing the least noble metal to deteriorate. Yes Robert it
    does happen, even if you haven't noticed it in your 40 years in the
    trade.;) Any resistor experts out there? Why are most resistors I have
    seen not made out of copper? Must be some reason.
  2. Jackcsg

    Jackcsg Guest

    Are you serious?
    If you are....Radio Shack may have the answers you need. Their answers may
    even be within your realm.
  3. Beachcomber

    Beachcomber Guest

    Well for one thing, the same reason why the overhead wires that are
    strung down the road are not made of copper. Copper corrodes when
    exposed to air. The other reason is that copper is a conductor - if
    you want something like 10 ohms or so, that is going to be a pretty
    thin wire.

  4. Mel

    Mel Guest

    Low wattage resistor leads are typically tinned copper, not aluminum. The
    leads connect internally to the resistive part which is usually carbon film.
    In the old days, it was carbon composition.

  5. Why do manufacturers give us resistors
    It's not a problem. If you properly solder copper wire to standard EOL
    resistors there will be no degradation at all.
    They're not made of aluminum.
    No, Phil, it does NOT happen if you properly connect them, even in if you
    think it will in your 40 weeks in the trade. :^)
    Commonly used EOL resistors do not cause problems when placed in contact
    with copper. BTW, I don't claim 40 years in the trade -- only 28.


    Robert L Bass

    Bass Home Electronics
    2291 Pine View Circle
    Sarasota · Florida · 34231
    877-722-8900 Sales & Tech Support
  6. I've been mucking about with building electronic stuff since I was old enough to hold a soldering iron..probably 40+ years and I've never seen a resistor corrode. However, we may have to consult with our resident guru, Paulie, maybe he has discovered GCR too.
  7. I've been mucking about with building
    Me neither.


    Robert L Bass

    Bass Home Electronics
    2291 Pine View Circle
    Sarasota · Florida · 34231
    877-722-8900 Sales & Tech Support
  8. mikey

    mikey Guest

    Greenish hue, sometimes rust like color, whitish on boards. I've seen it,
    especially on stuff what got wet. Where's Jim? He works on boats,
    fascinating what he goes through to protect shit.

    I've been mucking about with building electronic stuff since I was old
    enough to hold a soldering iron..probably 40+ years and I've never seen a
    resistor corrode. However, we may have to consult with our resident guru,
    Paulie, maybe he has discovered GCR too.
  9. Dr. Phil

    Dr. Phil Guest

    Thank you Mikey. I knew I couldn't be the only one to have noticed this
    .. Although I am very observant. ;)
  10. yes, ive seen that on window contact connections when the connection has been wet for a while..drywall wet connection wet...grows the copper crystals which end up just conductive enough to create a swinger - probably is a electrolytic reaction between the copper wire and something in the drywall compound.

    never have seen it on resistors though.

  11. Tell us more about the Battery Diode Harness Story
    Bass and the Battery Diode Harness StoryFrom: (Group
    Subject: REPOST: Battery Diode Story - GOOFY BASS WRONG AGAIN
    Lines: 89
    Date: 22 May 2002 07:13:17 GMT
    Organization: AOL
    Message-ID: <>

    This is the guy ROBERT L. (Lunatic) Goofy Bass that his Clones think he is
    knowledgeable about alarms.

    Battery Diode Story

    Bass Was Totally Wrong - This was taken right from
    Subject: Re: Connecting more batteries
    Date: 2002-04-08 07:38:27 PST

    > > > >

    I think you've got this one wrong, friend. Napco provided a Battery Diode >
    when > > > > I installed their add-on power supply. In fact, it's still
    on the > > > > ADI server as a valid part, although AFAIK Napco has stopped
    producing them. > > > > > > > > If you make current flow in the wrong
    on a battery charging > > > > circuit you'll have a lot more than a dead
    battery to worry about. To test > > > > your theory take a discharged
    and connect its terminals to another, > > > > fully charged battery with the
    terminals reversed (so you can get current to > > > > "flow back into the
    battery"). All kidding aside, don't really try > > > > this. The results can
    include fire and explosion, depending on the type of > > > > battery and its
    condition. > > > > > > > > BTW, the charging circuits on many alarms are
    actually 13.8VDC -- not 12 > > > > Volts. > > > > > > > > Regards, > > > >
    Robert L Bass > > > > > > > > =============================> > > > > Bass
    Electronics > > > > The Online DIY Alarm Store > > > >
    http://www.Bass-Home.comSales & Tech Support > > > > 941-925-9747 Fax > > > >
    This is the CORRECT answer
    Again taken from

    > > > Sorry, Robert,
    but it looks like you have this one wrong on two counts > > > and Nomen
    is right on the money. Like you, I have also done > > > countless
    multiple-battery MA3000 commercial fire and burg installs > > > over the
    years.optional PS3000 power supply, but do need to supervise for AC > > >
    This module connects the PS3000 jack to the AUX relay, which > > > is
    upon brownout. > > > > > > Secondly, the Dual Battery Harness, to which I
    believe you were > > > referring in your post, does not have a diode in it
    all, it simply > > > parallels the battery leads to allow the connection of
    or more > > > batteries to the MA3000, or any other panel. > > > > > > I do
    think UL would require a diode in the battery harness that > > > would waste
    valuable 0.7 VDC in a low battery condition just to > > > protect against
    installer reversing the battery leads > > > accidentally. There is already a
    thermal circuit breaker on the board > > > for this type of protection. > >two directions, you will soon have a very dead battery. > > > > > > Best
    Regards, Oleg


    Nomen Nescio wrote: > > > > > > > > > > Better not use a diode to isolate
    two batteries. Remember, current has > > > > > to flow both directions on a
    battery lead: into the battery when it's > > > > > charging, and out of the
    battery when it's discharging. So if you orient > > > > > the anode towards
    charging terminal and the cathode towards the > > > > > battery, the battery
    will charge but will not be able to deliver power to > > > > > the system
    the AC is off. If you orient the diode the other > > > > > direction, the
    battery will not charge. > > > > > > > > > > Diodes also have a 0.6 volt
    across them, so if you charge a battery > > > > > through a diode, you are
    getting the full charging voltage. > > > > > > > > > > Use a fuse or circuit
    breaker instead, preferably the harness provided by > > > > > the panel

    SO those who want to take Goofy Bass's advise because you think he knows
    thing -THINK TWICE.

    Mike, Sr.
    Alarm Services Inc.(NJ)
    Group Moderator

    Visit The Goofy Bass Website
  12. John O

    John O Guest

    I've been mucking about with building electronic stuff since

    I have never, ever seen a resistor lead corrode without some serious outside
    influence, such as a nearby leaking battery, salt water, or some such. We
    have some 50+ year old Heathkits up in the loft...and I bet we wouldn't see
    any corroded leads in there.

    I saw some extensive life testing of such things at Zenith, and the only
    thing that wrecked proper solder connections (and the resistors themselves,
    obviously) was excess heat. We did see that white powdery stuff, and one of
    those engineers could probably explain what it is, but I recall it happened
    as a result of some time in a humidity test chamber. IIRC it was left behind
    by the moisture that condensed and then evaporated.

    -John O
  13. Dr. Phil

    Dr. Phil Guest

    maybe that is what it is that I have noticed, may be electrolytic
    instead of galvanic or maybe a combo?
  14. Jim

    Jim Guest

    On boats there's always some kind of galvanic action going on

    For those who are not boaters, (especially in salt water), if you want
    to have any propellers, rudders, or any metal that is in contact with
    the water, left on your boat, you'd better make sure all metal object
    that are in contact with the water, are bonded ( attached with a heavy
    wire where they protrude inside the boat) to each other and that you
    have sacraficial zinc's attached to the underwater metal objects. These
    pieces of zinc are made of a compound that will erode quicker than the
    bronze, brass, or stainless steel that they are attached to. It's also
    important to check them during the season because if they should erode
    faster than normal, it's likely due to an electrical problem with
    either your boat, another nearby boat in the marina or with the
    electrical service on the dock. There are always the horror stories
    about people who havent checked and have had portions of their engines
    errode away. There are even zinc rods that have to be inserted into the
    cooling system flow, since much of it is isolated from the
    (grounded/bonded) engine block by waterjacket gaskets but is still in
    touch with the water.

    As far as electronics goes, I've never seen it on my boat, since I seal
    everything that is worth protecting, and remove all electronics during
    winter layup. Marine electronic products are sealed and boards are
    sprayed with sealer. But on other boats, where owners are not so
    protective, sometimes an electronic device can be affected by this
    white (corrosive(?) powder. Items such as TV's and devices not
    especially made for marine use, have a reduced life expectancy.

    Generally un-anodized aluminum does "powder up" ie. corrode in a salt
    atmosphere. I've also seen "white powder" on electronic components but
    I assumed it was just due to the residual salt in the atmosphere
    reacting with components in the metal leads and possibly causing some
    electrolysis. I've thought that most of the electronics, being low
    voltage/current, would therefore cause a small amount of electrolysis
    due to the salt air.

    I don't know if there's a connection between the aluminum white powder
    and this white powder, or not. Perhaps due to the solder on the
    leads.(?) When salt water gets on electronics, there's the typical
    green corrosion, which I assumed was from any copper present and
    there's usually a white powder, which I assumed to be some combination
    of water, salt/elements in the water, reacting to the presence of
    electricity and other dissimilar metals ie. electrolysis of a different

    I've never seen a resistor lead corrode on a land side site without
    some sort of catalyst or outside influence. It occurs to me that heat
    caused by a to small a wattage resistor, in a moist/humid atmosphere,
    might cause corrosion to occur at the lead/resistor juctions. Also, are
    all resistors of equal quality? I'd imagine that there are some really
    cheap resistors out there that are made out of compressed mud and
    bamboo. Could be bamboo sap you're seeing.
  15. a cheap and quick preventive action to the Galvanic Reaction is to coat the
    electronics or exposed parts with candle wax. just burn the candle and let
    the wax drip onto the parts.

    I've seen some manufacturers use the trick to "so call" waterproof there

  16. I have never, ever seen a resistor lead corrode
    Perhaps if you prepended "Dr" to your USENET nickname your experience would
    be different. Ordinary technicians -- those who don't submerge there alarms
    in seawater -- never see resistor wires corrode. Then again, no one I know
    uses resistors with aluminum leads. :^)
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