Quoted message said:I'm curious if anyone knows what the actual claim is--does
WD-40 (supposedly) work by chemically working its way in
between metal and water, by combining and carrying the water
away when it evaporates, or just by mechanically scouring
the moisture off the metal when blasted at the parts?
The claim made on the admittedly old can of WD40 in front of me is:
WD 40 DISPLACES MOISTURE
Drives moisture off metal surfaces.
-Distributors -Relays -Switches
-Wet engines -Spark plugs
I can attest to the fact that an engine which has been drowned
sufficiently due to driving through deep puddles will often have
moisture beaded throughout the inside of the distributor cap. In that
situation, the spark from the coil will simply discharge across the
moisture film to the distributor housing, rather than jumping the two
air gaps in the normal discharge path. Merely wiping the cap out with
a dry cloth *sometimes* will allow the engine to be restarted, but
often this is not sufficient. Spraying the inside of the distributor
cap with WD40 will usually cause the moisture to bead up and flow off
the surface; apparently at least some of the fractions in WD40 have a
higher affinity for the plastic and metal surfaces than water does,
and can "get under" the moisture to some extent. It may also be that
WD40 may increase the dielectric constant between the various isolated
moisture beads and patches, interrupting the alternate path to ground
that the moisture was providing; they make no claim about that, but it
seems likely that it would have this effect.
On the other hand, despite the claims made on the can, in my
experience WD40 evaporates too fast to provide any kind of long-term
(or even medium-term) moisture exclusion and/or rust prevention
factor. I've seen acquaintances use it to get wet engines started
many times, and have used it that way myself as well. If the
distributor cap is removed from the hot engine again a few hours
later, there's nary a trace of the product to be found. When I lived
in sodden South Florida, it was considered simple prudence to carry a
can of WD40 under the driver's seat of one's car. While the puddles
there were seldom deep enough to cause water to come in when the door
was opened, the frequency of torrential rains was such that it was not
so much a matter of whether a vehicle was going to have moisture
intrusion problems in the ignition system as when...and how often.
Unsurprisingly, such an under-seat WD40 can itself was almost always
rusty, despite having had more than a little of its own contents end
up on the can when in use.
As noted in other posts, I am not a fan of WD40 for the majority of
its claimed uses. I have found that it will "stop squeaks" only
briefly, I have noticed that it is rather poor at preventing corrosion
on metal surfaces, and I have been unimpressed by its properties as a
penetrant for loosening rusted fasteners. On the other hand, as a
solvent to get certain waxy or tarry deposits off of a surface, and as
an aid in either displacing or isolating water from an ignition
system, I've found it just useful enough to warrant keeping a can of
it around. The one in front of me was bought in 1979, if I am not
mistaken. I don't use it very much...and there are places where I've
learned that it's worse than nothing at all, such as on the threads of
a puller.
--
Typoes are a feature, not a bug.
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