I'm looking for a non-destructive test to identify spoke material between stainless steel & UCP ZINC STEEL (plated steel). I'm sure stainless steel is nonmagnetic but what about the plated spokes? If not by magnetism is there another way to test spokes?

I go by the magnet test. Stainless steel spokes are very weakly magnetic. The plated or galvanized spokes are normal magnetic, like the spokes will stick strongly to the magnet.

Also color, generally stainless spokes will clean up nicely and look pretty. The galvanized or plated spokes generally are duller and have a more spotty finish.

The magnet is the definitive test for know if spokes are stainless or carbon/alloy steel. As noted many stainless alloys are slightly magnetic, but it's day and night between those and plated spokes.

Zinc plated spokes are typically treated with a clear chromate conversion layer which has a bluish hue compared to the medium silver color of stainless.

This is a bit OT but hopefully informative. The answers that stainless steel spokes are nonmagnetic are correct because the stainless used in spoke manufacture (most commonly AISI Grade 304) is an austenitic stainless and, therefore nonmagnetic. So while a magnet is a definitive test for stainless steel spokes it also won't attract the far less common aluminum spokes (trade named Zircal) Mavic used on some of it's boutique wheels and the also rare and very pricey Titanium spokes that were trendy a few years ago.

Further OT, not all stainless steels are nonmagnetic. The 300-series (303, 304, 316, etc) used in spokes and for many industrial products for it's high corrosion resistance is nonmagnetic. However, the 400-series (410, 416, 440, etc., aka stainless "tool steels") used for cutlery, tools and similar products are fully magnetic and cannot be told from regular carbon steel by using a magnet.

FWIW. I've used some 316 SS tubing that was magnetic in the hard un-annealed state.

Yeah, severe cold working of the 300 series stainless steels can make them weakly magnetic.

Read the end of the box the spokes come out of , when you built the wheel, is the obvious way

Doesn't work very well if you are dealing with an existing wheel.

yea , but there is no guessing .. lots of guessing ,above.

I can tell Zn from stainless by looking at it .. Zn is not going to be shiny by now ,
stainless wire is now dominant in new spokes these days ..



I've helped weld big ingots of Zn cast around a steel flat bar, onto Ships..

it It's done as a sacrificial metal to be a reduction to seawater attacking the steel hull .. itself.

Exactly, all the spokes I'm checking are used salvaged from bent rim wheels, probably should have mentioned that.

Mak a pile of all the spokes and move a decent magnet among them to pick up and remove whatever spokes it will. Those are plated steel, what's left is stainless.

Yes, there are magnetic stainless steels but they aren't commonly used for spokes (if at all).

Once you've sorted by material, then separate the butted from plain gauge, then sort by gauge and length.

Plain gauge & butted, what's the difference?

From https://sheldonbrown.com/wheelbuild.html

"Spokes come in straight-gauge or swaged (butted) styles. Straight-gauge spokes have the same thickness all along their length from the threads to the heads."

"Double-butted spokes are thicker at the ends than in the middle. The most popular diameters are 2.0/1.8/2.0 mm (also known as 14/15 gauge) and 1.8/1.6/1.8 (15/16 gauge)."

Thanks for the info. I think I saw those (double-butted) on a wheel once but I never get any like that.

Oddly enough, I have come across quite a few stainless spokes that are faintly magnetic. I use an extremely powerful neodymium magnet that will cause blood blisters if you let it attach to a metal surface with your skin in between. Those magnets seem to even attract stainless spokes but just barely. Like it will cause the spoke to move a bit to the direction of the magnet but won't be able to be picked up by it.

Again, the weak magnetism of otherwise austenitic stainless steels is caused by cold working the metal during drawing and swaging to form spokes. However, a magnet's attraction for these is vastly lower than for standard non-stainless steel spokes and the difference should be obvious.

Virtually all budget priced factory wheels come with straight gauge spokes so, if you're working with a pile of used spokes, that's probably most of what you have. I can tell the difference more easily with my fingers than I can by looking. Start at the elbow and wipe your fingers down the spoke.

Yes, as I mentioned in my first post about magnetic properties, stainless spokes have vestigial magnetism. But no nearly enough to be picked up.

Once anyone picks up a single plated spoke with a magnet, the difference between being truly magnetic, and barely so is as obvious as day and night in the desert.