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Advisability of using anti-corrosion lubricant on contacts

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nuckolls.bob(at)aeroelect
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Posted: Thu Jan 03, 2013 5:34 am Post subject: Advisability of using anti-corrosion lubricant on contacts

At 10:58 PM 1/2/2013, you wrote:

 --> AeroElectric-List message posted by: "bobbarrow" <bobbarrow(at)bigpond.com>



  What kind of connectors and what finish  on the pins? 



 Power through Mil-C-26482 circular connectors with M39029 crimped contacts.  Signals through M24308 DSub connectors with M39029 crimped contacts.



 The M39029 contacts are typically gold plated copper alloy. However the female contact for the circular connector seems to have a stainless steel socket.



 I have Corrosion X and  LPS 1, 2, and 3 in stock.



 I note that the spec on Corrosion X says it can be applied to "electrical and avionics components such as micro switches, Cannon plugs, antenna bases, circuit breakers, and bus bars.



 The warning on Corrosion X in aircraft pertains to a research paper into the the affects that the lubricity of Corrosion X could have on friction mated structural components in shear. Nothing to do with use on electrical components.



 I also have the normal run of behind-the-firewall connectors in the form of spades and ring terminals (forest of spade tabs for ground, bus bar ring terminals etc). These might benefit from some corrosion protection as well.



 What do you think. Is a little corrosion X in order.



  Qualification for the connector materials you've cited is rigorous. Their suitability to task has be demonstrated by decades of service history in a full range of applications. I cannot recall having encountered a connector failure due to environmental stresses within limits for which the connector was designed. Connectors fail mostly due to installation error or gross abuse that would affect not only the connector but much of the system hardware around it.

  Other than addition of moisture displacing 'stuff' in the faying services of bolt-up joints, I see no value in application of 'more protection' for a condition that has no demonstrable risk. Indiscriminate use of such products seems more likely to raise risks for unintended consequences (like just plain messy) than to mitigate real risks.

    Bob . . .    [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jan 04, 2013 7:18 am Post subject: Advisability of using anti-corrosion lubricant on contacts

At 07:06 AM 1/4/2013, you wrote:

 	  Quote: 	
		  

<public(at)toddheffley.com>



Wow....Talk about the subject that will not die!


	


   Not sure why anyone would want it to 'die' . . .



 	  Quote: 	
		  I have watched this controversy in my industry (large cabin 

executive jet maintenance) for some time now, and much like the 

discussion here, it will not die.



Some airframers do not want corrosion inhibitors between the antenna 

and the airframe.



Conversely,  I worked for a MRO that requires Pentrox Type 2 (grey) 

for every antanna installation. (conductive paste, feels like 

toothpaste, non-hardening)


	


    There's a BIG difference between the situation you

    are citing and the conversations we've had here on

    the list.



 	  Quote: 	
		  My anecdotal experience tells me that antenna footprints are the 

first and worst hideouts for corrosion on many aircraft. 

Particularly lower antennas.  My experience is 1 to 1 without 

exception. If a removed antenna has Pentrox under the foot print, it 

has no corrosion. I come down as a strong advocate for adding Penetrox.


	


    Absolutely. But the identification of successful

    remedies for specific issues does not translate

    into a general applicability as a prophylactic

    measure. I.e. using Penetrox to offset a specific

    vulnerability does not suggest that dipping the

    whole airplane into Penetrox is a good idea.

 	  Quote: 	
		  I have two theories: one is that Airframers live in perfectly clean 

factories with brand new airplanes that never corrode. Antennas are 

installed on perfectly clean ground planes, and that thinking is 

inviolate. MRO's live with 30 year old airplanes, thus the 

difference between the two.



Theory number 2 is that the clamp up force of an antenna is very low 

because of the large size of the footprint. Use of some type of 

"magic goo" seems more reasonable, because one can never achieve 

a  vapor tight fit up over the entire footprint of the antenna.



I doubt there is a wooden stake for this vampire, but I would like 

Bob's thoughts related to HBC background vs. OBAM background.


	


    Some years ago I published this drawing



http://tinyurl.com/6rwodso



   that spoke to the value of high mate-up forces

   in the vicinity of mounting hardware along

   with a suggestion that paint be removed from

   skin ONLY around the holes. It was a toss-up

   then as to how moisture might be prevented from

   taking up long term residence under the antenna.



   THIS is a problem. I suggested a bead of RTV on

   the outside because it can be inspected and renewed

   as needed. A gasket is NOT called for because it upsets

   the design goal for gas-tight bonding at the bolt holes.

   Silicon grease would be good for protecting the bonds

   and is probably the preferred technique . . . but that

   stuff is a high viscosity liquid with very good wetting

   properties. This means that the stuff migrates out from

   under the antenna base and stains surrounding surface

   while adding dust collection. Looks like (at)#$(at)#.



 	  Quote: 	
		  I come from a maintenance background , not a build background, so 

....grain of salt....


	




   So you're quite right that there's a unique and

   challenging problem to seek the elegant process

   by which long-lived antenna installations can

   be made . . . certainly more than a 'grain of salt'.



   In retrospect, given that electronic grade

   RTV in the uncured state has no significant

   compression strength, It would be interesting

   to try an overall, liquid gasket approach

   under the antenna using the silicone sealant.

   I think it would extrude out of the gas-tight

   contact areas as the bolts are torqued up. Squeeze-

   out around the base is easily cleaned after

   the bolts are tightened. Overall water tightness

   should be quite good.



   I'll put that into my list of experiments to

   try . . . One could overlap 3" wide strips of

   say 1/8" and equivalent thicknesses for skin

   and doubler. Do the 'bonding' thing around 4

   holes with 10-32 hardware in them. Dope the

   interface between 1/8" and 'skin' with rtv

   and clamp it up.



   Do a test on bonding integrity of the two

   surfaces after the RTV has cured. Repeat

   without RTV and compare.

   Bob . . .

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