Plug ground strap

[ojh]

We use autolite 3932 & 3931 plugs. I've noticed that the ground strap on some of the plugs has a yellow tint, almost like a haze that you could wipe off - but you can't. There isn't anything remarkable going on in the holes that this occurs in, the rest of the plug looks pretty much like the others. The other plugs' ground strap look like raw steel and easy to spot timing, very clean. These look much like soft steel with a lot of sulpher, i see this coloration from time to time welding, it'll show up around the edge of the heat zone.
We have a 12deg 632, 2 stages #32 n2o pill, maxnos fuel.
Have you guys seen this? Has autolite lost its' consistancy from plug to plug? Is there something going on i should be aware of? What would you guys do, or have done?
Thanks for the help, oj

[John_Heard]

Are you getting some Autolites with a coated strap now? I thought they used to be uncoated, but maybe they have changed? What you're probably seeing is the ground strap coating burning off. Maybe you got a mix of new and old plugs with diff coatings on them?

[ojh]

Coatings? I bet you are right, so the holes with the yellowish tint have yet to get as hot as the holes with the bare steel strap? All else being equal, the hole with yellowish tint would be on the more fat side? Is that how you would read this?

[John_Heard]

Yes, the yellow is probably coating burning off. I'm not sure what that coating is, maybe zinc of some sort.