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Copper vs Aluminum crush washers

Joined
21 May 2006
Messages
1,226
Location
Basking Ridge, NJ
Many parts stores carry copper crush washers in various sizes.

Any metulurgists out there who can comment on the galvanic potential difference and the impact on corrosion, etc, for an aluminum vs copper washer between the following bolt and case/pipe combinations:

al to al (coolant pipe washers)
steel to al (transmission drain/fill plugs)
steel to steel (oil pan drain plug)

(From my career in telecommunications equipment electronics design, on anything exposed to weather the mechanical engineers would have never used an aluminum washer between with steel bolts and steel metalwork because of severe corrosion issues. The cabinets & enclosures had to survive 20 years in harsh coastal salt fog environments. Hence, my curiousity on this topic.)

Also, with a possible difference in hardness, would copper affect the tightening torque? I've seen/used copper washers on non-NSX/Honda oil pans that use lower tightening torques, and they worked well. Would the copper creep under pressure from the higher tightening torque?

I've always gone with the aluminum for my NSX, but it sure is convenient and cheaper picking up a pack of copper washers at a local parts store.

Frank
'91 NSX-T, red/tan
 
really makes no difference.

have changed oil in ..... many many cars, rubber, copper, alun, no gaskets. if torqued down to the right specs they dont leak. even when you re-use the old one. :smile:
 
I have used both copper and aluminum washers on all my Hondas/Acura. I don't think it matters if you change the washer with every oil change. I have also reuse the washer by flipping the washer around when I am out. Corrosion takes time and if you change you washer before corrosion starts, it doesn't matter. I normally buy 20 washers at a time from either the Honda or Acura dealer. Having 3 Hondas/Acura, I go through them pretty fast.
 
An old trick in reusing old metal washers is to anneal them. Essentially, heat the old washer until it's red hot, then let it cool. By doing this, the metal expands to it's original size and will work like new again.
 
Doc, you're never going to get aluminum or aluminum washers red hot. :biggrin:
 
Oops--I've always done this with the copper squash washers for a Ferrari.

Q--even if the aluminum ones don't get red hot, will the principle still apply--ie will they expand to original size?
 
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