Fuel tank problems

[Baffled]

Hello, All. Has anyone got any experience of this problem: the lining of my fuel tank has erupted into a, hard, brittle, flaking shell-like substance. It is mid-brown in colour and shiny and quite resistant to picking it off with my fingers (not that I can poke them far though the filler hole). I have bought a tank repair / relining kit from POR15, which includes a washing chemical to dissolve and remove varnish and other deposits. I haven't used it yet, but I have to say I have my doubts over whether it will shift this muck. Any ideas, anyone? Yours, Baffled.

[hendre]

first go at it with mechanical means, put bearing balls in the tank and let it rotate (pack it in a thick blanket and stuff it in a cement mixer) for an hour or more... this way most of the hardened stuff will be loose and you can take it out with a vacuum cleaner. This way your dissolver will be so much more efficient in taking out the remains...

[EVguru]

the lining of my fuel tank has erupted into a, hard, brittle, flaking shell-like substance. It is mid-brown in colour and shiny and quite resistant to picking it off with my fingers

Sounds like Petseal. It didn't have the best reputation even before the latest round of fuel changes.

There are specific Petseal removing formulations available.