Scott, Rocco, Dennis:
The experience and learning the Air Force has accomplished in the last 15 years about corrosion in electrical connectors
may be of interest and substantial benefit to all of you.
The F-16 fighter is a marvelous machine, but it has significant corrosion problems with electrical connectors even with
Mil-Spec hard gold/gold plated connector contacts.
In addition there are both fretting and galvanic corrosion with connector sets with tin plated pins matching to gold
plated sockets. One aircraft crash cited short circuits in an electrical connector as the probable cause.
There is persuasive evidence that more mishaps have been due to corrosion and short circuits or high resistances in
connectors.
In fact, there is persuasive evidence that other USAF aircraft have had multiple mishaps due to connector corrosion.
The AF has contracted with Battelle Memorial Institute in Columbus to study the problem, and the results of considerable
testing reveals all electrical connectors may be at hazard for corrosion.
And they identified an inexpensive, easy, and long lasting solution. This started in 1986 when an aircraft was on final
approach into a Texas air base, and the engine flamed out.
The most dangerous times in flight include takeoff and landing, but the pilot was able to glide far enough
to land on the runway overrun and roll to a stop. That started an expensive but very profitable research program
that the AF now is nearly prepared to implement treatment of F-16 connectors and already has begun to implement
on some other aircraft. The connector treatment implementation is expected not only to significantly improve safety,
improve the aircraft reliability, increase the mission capable status of the aircraft on the ramp but also reduce
number of computers, radar, communications and other boxes that are sent to be overhauled.
That reduction in sending boxes to be overhauled in a 2.5 year study resulted in the cost savings
averaging about $600,000. per aircraft per year at one base where that data were analyzed.
It also reduced the maintenance man-hours about half for those aircraft treated.
Battelle found that half of the products being sold to the DOD to prevent corrosion in electrical connectors
actually accelerated corrosion in some tests all of which (except one) were qualified under the Navy's specification
MIL-C-81309.
Battelle contacted all the companies that claimed their products were corrosion inhibitors but caused corrosion,
and none of them had done any testing to substantiate their outrageous claims. However, Battelle identified
MIL-L-87177A Grade B (invented by the Bell Labs for their own use) as an excellent corrosion inhibitor for connectors
that lasted for a full two years.
Fred Meyer at the AF Materials Lab heard about it and wrote a specification to describe it. In fact, that 2.5 year study
was done on gold to gold connectors only, and the mean time between failures of black boxes
(called line replaceable units = LRUs) was extended as much as fifteen times (on the flight control computer).
That is a spectacular improvement, and the mission capable status was improved 15%, also spectacular.
Not known to the AF at the time the Dept of Energy that has some association with ICBMs tasked the Sandia Labs
to study so called corrosion preventive compounds and came to a similar conclusion as the Battelle Labs.
On the Sandia team was the former Bell Labs scientist James T. Hanlon, an Extra Class Operator, W8KGI.
The final report of their study was entitled, "MIL-L-87177 Lubricant Bulletproofs Connectors Against Chemical
and Fretting Corrosion."
The following characteristics show why it is such a super corrosion preventive compound (CPC).
It has a very low vapor pressure so that flying up to 70,000-feet will not cause it to evaporate and disappear.
It is liquid from -70-deg F to 550-deg F.
The surface tension of water (moisture from the air, too,) is high so H2O tries to go into a sphere,
but the MIL-L-87177A Grade B has a low enough surface tension that it can go right under the water
here there is a slight void and expel the moisture in cracks and holes in the metal.
It is not miscible with water so thereafter the moisture from the air cannot penetrate it and get to the metal.
The Royal Navy has found that even electrical connectors in their salt water "bilge" tanks that are emptied
to surface and filled to dive are unaffected by the salt water; they love this stuff.
Also, some of the F-16 users who participated in the test program still are using the material although the test program
is over, because they saved so much time, improved their mission capable rate so much,
and saved so much money.
No damage to connector materials has been seen, and the chemicals all have been tested to assure
no hazardous effects to the users. I recommend NASA look at using this CPC, because it promises to reduce
their corrosion problems significantly and perhaps end the corrosion connector problems altogether.
The same goes for all of your amateur radio connectors. I buy it for my coax outside and treat all the connectors
in my shack and my computer connectors and card edges.
It not only acts as a fail lubricant to prevent gold smearing but also prevents the gold and all other metals from corrosion.
Battelle found that enough corrosion occurred with gold to gold connectors to cause intermittents and shorts in only six
months. What really happens is that the copper or the nickel under the gold sees the gold as a dissimilar metal and is
corroded by the more noble gold.
The gold probably does not corrode.
The National Stock Number for the MIL-L-87177A Grade B is 6850-01-328-3617, ( updated 2006 to 6850-01-528-0653) and a qualified vendor is Lektro-Tech, Inc,
2300 South Dock Street Unit 102, Palmetto, Fl 34221, 813-831-4006, fax-813-831-1238 e-mail: marketing@lektrotech.com.
It is a little expensive, but we calculate we are saving in the realm $500. to a thousand dollars for each penny spent
on the CPC.
David H. Horne, P.E., WA7LJU
-----Original Message----- From: Scott Johnson Sent: Saturday, November 08, 2003 9:33 AM
To: Collins; Rocco Lardiere
Subject: {Collins} Re: gold connectors the problem is that the gold flash on the cheap connectors is not thick enough
to server as a barrier coating, and in many instances it is not even gold, it id titanium nitride which is a crappy conductor
----- Original Message ----- From: "Rocco Lardiere"
To: ; Cc: Sent: Saturday, November 08, 2003 9:20 AM Subject:
Re: {Collins} Re: gold connectors > Dennis, > >
I agree with you that the high dollar audiophile connectors and cables are a > waste of money.
However, in my radio room I use gold plated RCA plugs (as > cheap as I can find them,
which is reasonably cheap these days) for one > reason - they don't corrode.
Most of the 60's and 70's equipment, including > Collins, that do not use gold or silver will have corrosion problems at
their RCA jacks. As you know, silver works very well, even if tarnished (a > good swap meet hint, by the
way), but silver RCA connectors are > "unobtanium." Pure gold is a bit softer, but the alloys used commercially
seem to hold up on the RCA plugs, and you can find these plugs easily.
I live near the ocean (Palos Verdes), and gold and silver connectors will hold up - most everything else WILL
corrode and cause trouble over time > (speaker output connections seem particularly vulnerable).
The gold seems > to be very compatible with the S Line jack materials (no problems with
dissimilar metals that I have seen - the gold will not react).
I also work in avionics engineering on satellites and launch vehicles; we sell to NASA, the DOD, and commercially.
Connector problems are a real > threat. We use gold pins and shells on the connectors, because the marine
salt air at the Cape Canaveral and Vandenburg bases will attack anything it can get to, and the gold will work reliably
in that environment - and is > easier to inspect when we need to.
Our circuit boards can be conformally > coated, but the connector surfaces are exposed to the atmosphere for months
or years. With many thousands of connections in a vehicle, the gold saves > us millions in downtime for
troubleshooting and repairs, not to mention the > providing the reliability we need when launching a billion dollar payload
(you only get one chance).
Believe me, we do not specify gold connectors > because they look nice or have slightly better conductivity - it's all about
the reliability and inspectability (no silver tarnish to confuse the issue).
Test equipment and computer manufacturers will use gold on selected > connectors for exactly
the same reasons, and they (and we) are under intense > pressure to cut costs wherever possible.
Reliability sells products, as Art > Collins well understood; that holds for the rocket and satellite business,
as well. > > I use gold RCA connectors in the shack because they work reliably over
the > years. At work, we do not use RCA connectors in an environment that > includes vibration and shock -
there is no positive connector retention feature - just the friction of the shell fingers.
But my radios just sit > there, so RCA's work well at home. The KWM-2 mobile scheme would also >
physically prevent the connectors from backing out, but that's an unusual application.
The KWM-1 connector assemblies also lock down the molded-in RF > connectors indirectly,
which may have led to the idea of the KWM-2 mobile > mounting design.
The comments on the cheap insulating materials used in some of these > connectors are on the money.
The cheap stuff melts at high power levels and > frequencies. However, I have never had a
problem at HF at the 100/150-W > levels that Collins exciters produce.
What I have seen over the years is > failure of RCA plugs due to poor soldering and strain relief.
Some of the > newer designs with removable shells are easier to inspect, and you can > usually clamp the
braid and even the insulation to provide better strain > relief.
The connector impedance bumps are fairly inconsequential at these > frequencies; what DOES count on
some S-line interconnections is the total of > the distributed capacitance of the cable (ref the earlier threads regarding
cable type and length). > >
Those who fortunately live in a relatively dry environment (Redlands!) can probably get away with "garden variety"
RCA plugs. Deoxit can help eliminate pesky problems, and I use it on all my S Line RCA
jacks.
I "exercise" the jacks when I refurbish a unit by doing several mates/demates and rotations to provide a wiping action
at the contact surfaces.
This eliminates a lot of future grief when a person has way too many radios, including yours truly.
Just my two cents' worth. > > 73, > > Rocco N6KN
---- Original Message ----- > From: "Dennis Deaton"
To:
Cc: > Sent: Friday, November 07, 2003 8:35 PM > Subject: {Collins} Re: Nylon insulated connectors >
Scottt, Some time back (probably over a year) this same subject came up on > the
reflector. The question was asked then "Why the RCA jacks for RF?". > Well, > > in the case of the
KWM-2 there was really good practical reason. When > used > > with its mobile mount,
the transceiver was designed to mechanically and electrically mate simultaneously.
Making all necessary connections by > just > > sliding into the mount. The only other connection you have to
make is to > > plug the microphone into the front panel. Even the speaker was connected
through the NB antenna connection! No other connector (costing less than > > $500 apiece) could do the job.
Like you say. The high-dollar audiophile > > connectors (and the Monster cable that is used with
them) is a real waste > of > > time and money. If they were all that superior, we'd be seeing them in
military and space equipment. After a 31-year career as an engineer for > the > > DOD, I never saw any of these things in use.
Sure, NASA had many > components > > gold plated. But they were dealing with noise levels far below our 0.5 uV
levels for ham gear. And they could afford to spend $500 apiece of our > tax > > dollars for connectors.
Just like DOD's $500 apiece toilet seats. Garden > > variety RCA plugs work just fine if installed properly.
Dennis Deaton, WA6ACC > >
123 Hartzell Ave. > > Redlands, CA 92377
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