the nuts are sst under the black paint and polish up really nicely - it's the alloy portion that actually mates with the splined shaft that is the tricky part. they don't polish very well and quickly get powdery w/surface corrosion.

I"m not so sure  the nut is stainless steel;  the magnet sticks to that too (on my 280Z.)  It must be just a 240Z thing.

 

I read in another thread here that the MX-5 Miata has compatible wiper arms?

maybe it's different by year - the nuts on my 78 polished up to a mirror finish and have not dulled a bit after months of dd in all kinds of weather.

Maybe the '78 nuts are Titanium.  I think that's magnetic, and it doesn't rust like ferrous metals.

Titanium is not magnetic, it is a non ferrous metal.  Some stainless steel will not hold a magnet due to its high chrome content.

 

Bonzi Lon

Magnetism is not a completely reliable way to determine stainless from non-stainless as many stainless grades are magnetic.

So if it's NOT magnetic, it has a good chance it's stainless, but if it's magnetic, you still don't know for sure.

So there's no point to looking for the 'stainless steel' 240Z wiper arms, because any seller will tell you it is so it will sell.

 

Why didn't the other models of the same years as the 240Z have the stainless steel wiper arms?