How to achieve a discolored chrome effect

I’m currently modeling a 1978 Peterbilt 359. Here is the current WIP.


In an effort to be as realistic as possible, I’m trying to achieve the effect of chrome discolored by heat at the tips of the exhaust pipes. Here is the effect I’m going for.


And here is my current result.


My current node setup includes a gradient texture connected to a color ramp, which gives a nice fade-in effect, but I have no idea where to go from here to get a more realistic “burned chrome” effect. Any help in this area would be greatly appreciated, even if it’s to point me to a tutorial that covers this.

Here is my current node setup.


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Thanks! I’ll give it a shot and post my results.