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ACF-50 Anti-corrosion between block and alternator mount..

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nuckolls.bob(at)aeroelect
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Posted: Sun Sep 23, 2012 9:31 am Post subject: ACF-50 Anti-corrosion between block and alternator mount..

At 03:03 PM 9/22/2012, you wrote:




When I took the old alternator mount off the engine, I noticed there 

was some corrosion on the engine block under the alternator mount. My 

new alternator (B&C) gets its ground through the mount. Can I use and 

anti-corrosion film such as ACF-50 on the block before bolting the 

mount to the engine? Or will that place resistance in the ground path 

for the alternator?

   The only way to you add resistance to the joint with such

   treatments is when the higher resistance contaminant is

   as hard or harder than base materials (alternator bracket

   and engine crankcase).



   For example, we've discussed the manner in which anti-corrosion

   dopes work in crimped terminals on aluminum wire. A wire

   grip and wire strands might appear to be full of dope but

   after the crimp, the PRESSURES applied to deform metal parts

   with intent to create gas-tight junctures is so much

   higher the compression strength of the 'contaminant' that

   it's extruded out of spaces where the metal hits the road.

   As you transition out of those metal upset spaces, the

   remaining dopant is squished out and remains in the voids

   becomes a barrier to moisture laden air.



   Back in my two-way-radio-days we used to pack coax cable

   connectors on tower joints with Dow Corning DC-4, a

   silicone grease the consistency of wheel-bearing grease.

   The connectors were then wrapped with 3+ layers of

   plastic tape (which would only stick to itself due

   to slickness of the coax and connectors underneath!),



   Such joints opened years later might have the tape

   nearly falling off due to UV and weather effects but

   the joints inside were as-new pristine.



   Suitable dopant used on the brightly cleaned and ready to mate

   surfaces of your alternator bracket and engine is

   incapable of raising joint resistance where adequate

   metal-to-metal contact and pressures are achieved.

   Remnants of the dopant not extruded out of the

   joint remain in non-contact areas and provide the

   desired barrier for ingress of moisture.



   There's a host of suitable materials. Electronic

   grade RTV (no corrosive type) comes to mind as a

   material with high operating temperatures but soft

   enough not to 'glue' things together. Chemical

   conversion coatings will only protect a surface and

   have no ability to fill gaps and preclude moisture

   incursion. You use those chemical conversion before

   assembly then use gap-filing dopants on top of that

   for the golden joint.



   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Sep 23, 2012 10:13 am Post subject: ACF-50 Anti-corrosion between block and alternator mount..

At 03:32 AM 9/23/2012, you wrote:

 	  Quote: 	
		  



Michael,



Since nobody has responded yet...I will offer my .02



It is my understanding that products like ACF-50 are used to prevent

oxidation/corrosion from developing.  If the part is already corroded, I

would suggest removing the corrosion and then use the ACF-50 to prevent it

from returning anytime soon.  You may also look for a electrically

conductive paste that will seal out the oxygen.  There should be plenty of

electrical pathway capacity through the mounting bolts regardless.



Bevan


	


   Bingo! You get the gold star for this topic

   my friend. The paste or "dopant" need not be

   conductive for reasons I cited in the other posting.

   But their function is necessary to joint longevity

   and goes beyond repairs and protection of surfaces.



   Chemical treatment thicknesses are measured in

   diameters of molecules. Gap fillers have a much

   larger and equally important role to play . . .



   Bob . . .

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