What is this layer of crap in my corny??

[BlackTieBrewing]

So I soaked 7 of my cornies in Oxyclean for over 24 hours. 4 of them rinsed out clean and were fine but 3 of them have this gross gritty crap on the walls inside the keg that wasn't there before. It's really hard to get off and I'm just wondering if anyone knows what this is or has experienced this before.

 

[killian]

I'm not sure exactly what it is you are dealing with but I would try giving it a rinse with star san. I'm thinking it might be beer stone. Good luck

 

[JuanMoore]

+1 on the star san. That happens if you soak things in oxyclean for too long. A quick rinse with anything acidic should take it right off.