You fucked up. Get a new bar. We pay for our mistakes.
It's with great shame that I say my barbell went into storage for about a year.
It has gotten much more than damp during that time and the I.D of the sleeve has completely rusted onto the bar.
I know you wouldn't have ever needed to fix mistreatment of gym equipment this bad, but do you have any advice for how I should approach fixing this? I have tried wd-40, mallets from rubber through to carbon steel, and differential heating of the sleeve/bar with propane.
My plan is to either get it acid dipped or soda blasted once disassembled.
Joe.
You fucked up. Get a new bar. We pay for our mistakes.
Yes. He did.
But...
Take some diesel and some automatic transmission fluid. Soak the bar in a 50/50 brew overnight. Take it out and heat up the bar until it's too hot to touch--BUT NO HOTTER or you'll kill the heat treat!!! For reference, you can't hold on to 150F too long because it's too hot. That's about right.
Start tapping with a hammer all around the joint--smack the end of the bar a few times. I bet it will break free. We have also heated up parts with a torch and melted wax into the joint. It wicks in and lubes up the bond so it will free up. Once you get a tiny bit of movement keep working it. You're almost there.
Finally--don't do that again
Did you try vinegar?
Kroil and let it soak a few days, then I'd get on it with a couple of big ass pipe wrenches.
Try using Kroil, which is the best penetrating lubricant I've found. It was one of very few penetrating oils that would loosen up heat corroded fasteners on jet engines/industrial turbines when I used to maintain them. WD-40 isn't a penetrating oil really.
Next time spray it down with WD-40 BEFORE you store it, to prevent this from happening in the first place, an ounce of prevention and all that.
A couple decades ago one of the gun magazines did a comparison of different rust inhibitors, they coated pieces of bare steel with them and left them outside in the weather. The only thing that performed better than WD-40 was cosmoline, and WD-40 is MUCH easier to get off. Unless it gets submerged you should be fine.
Electrolytic Rust Removal Aka Magic: 10 Steps (with Pictures)
I know several people who have used this method and it works.