Aluminum Vs Steel Lug Nut Corrosion

[Carboy_GT]

Need to replace the old Aluminum lugs on my 944, a some survived but probably 10 of the 20 on the car will not be seeing the road again. 8 of the survivors are very corroded. I've got the 928 sewer lids on my car which are aluminum. I'm thinking of replacing it with steel but I wanna make sure the steel lugs don't corrode-weld themselves to the wheels. Any recommendations on a reasonably priced set of lug nuts and/or locking lug nuts?

al-vs-steel-lug-nut-corrosion-v0-rzlup3xa827d1.webp (129 KiB) Viewed 578 times

[dr bob]

Over the decades I've seen more than a few cases where a corroded aluminum lug nut needed to be removed with a hole saw from a manhole-cover 928 wheel like yours. It hasn't been an issue on mine since the wheels come off a few times a year for cleaning or service. Most serious problems seem to afflict cars that might go years between removals, on cars driven in rain/snow especially with some salt. Those equal galvanic corrosion as the anodizing is scrubbed off. Maybe another big factor is overtightening. There's plenty of speculation but the problem exists regardless of cause.

The 928 workshop manual is a little vague on preventive options. You can safely use a little anti-seize or grease on the cone/cup. Choose carefully, as an anti-seize or grease with graphite does you no favors with the anodized wheels and nuts. In my little spare time 25+ year retirement gig, I got to stand next to folks who do the serious mechanical work on large gas and steam turbines in power plants. They use a "nuclear grade" non-metallic or nickel-based anti-seize, one that seems happier in the 1000º+ environment. You can buy it on Amazon ($$) but a small can will last a really long time. A thumbnail guidance is to reduce the bolt torque by maybe 10% from the non-lubricated spec, but on wheel nuts that reduction may or may not be a great idea. I do it since the wheels are off regularly and the torque is checked each time. Use your best judgement.

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A decade-plus ago I had a set of VG S4+ manhole wheels re-anodized at a place on SoCal to restore the surface to new. I'd carefully stored the original wheels for my car with the original tires, and clinic visitor noted how his own wheels looked so much different. His had been cleaned with a mild-acid wheel cleaner, then treated to a mild abrasive polish to try and resolve the damage from the wheel cleaner. It looks like the wheel you picture has enjoyed some similar polishing/cleaning sometime in its past. So his were restored to new appearance. If your quest includes originality, there are places that can do it for you. The result is a satin gray finish that won't tolerate anything. The original recommendation from Porsche was to coat the anodized face with a film of Vaseline. Very practical...