Touché to what Myka and crimper said.... I was thinking yesterday of posting the exact same thing as crimper. If I lived closer I would come grab some salt from that bucket before you throw it away. I trust your experience also spitfire but think it would really be beneficial for you to give a sample of that to someone to test if you don't feel like it yourself. Or send it in to IO like Myka suggested, I'll even offer to pay the postage if you're over it
Really sorry to see this happen to your tank
Pretty sure that's the most popular brand of salt and type of salt used, so it could have an impact on a lot of people who switch brands of salt too quickly now because they're scared of suffering the same fate as you.
So please help the community find a reason, if it takes me driving out there to grab a sample then so be it, if you're sure it was the salt.