I have a bunch of turnbuckles I need to un-do and then re-screw. The all look about like this one. Rusty threads. I used PB Blaster penetrating oil on one of them so far and that worked for allowing me to unscrew/re-screw. This one and I'm fairly certain most of the others aren't coming so easy with the PB Blaster method. So I was gonna use a torch, try applying heat. Where's the best place to heat up, on the middle part that turns or the threaded part, or both? Any comments/advice appreciated.

 

You ideally need to heat where the threads go into the center piece as that's where the rust is holding you up.

Once you get them off......soak them in the solution directly. After several hours they should almost be as good as new. I buy the Liquid Wrench by the gallon but there are others that can do the job.

 

You could also soak them in phosphoric acid for a while....it'll eat the rust right off. Rinse with water, dry and ready for paint if you want to do that.

I think muriatic (pool) acid might do the same...but it's nasty stuff. Phosphoric is a bit easier to work with, but use a plastic container. You can buy it as "Metal Prep" in paint stores or big box stores. It's also the main component in lime remover in restaurant supply products for large kitchens.

 

I failed to mention I'm wanting to avoid having to cut and then re-crimp the loop and crimped ends of the cables to completely remove the turnbuckles from them. So in that case I'm not really able to take them off and actually soak them in anything. I'm wanting to loosen/re-tighten them in place where they are, the one end still attached to the cable. Getting ready try the heat. Will post back with update. Thanks.

 

I've found that an mix of acid, soap and synthetic grease works as an alternative to soaking in acid. Chemistry degree at work ...

Soap (aka fatty acid) has one end that likes oil, while the other likes water.
Oil interacts with soap's oily end, leaving the water loving end exposed, which results in tiny blobs of oil that can disperse into water. It also works in reverse, so that tiny blobs of water based solutions like acid can be disperse into oil or grease.

Soap allows the acid to dissolve into the grease. The grease seems to "creep" along the threads and then the acid removes the rust.

 

If it were me I would just open the eye on the turnbuckle and remove it from the cable. Toss the turnbuckle in the recycle bin and replace with new. You will spend more on chemicals and wasted time than for new turnbuckles.

But that's what I would do. I'm not you.

 

I checked at the local hardware store and they want about 10 bucks a pop for new turnbuckles this size. I can afford to spend a little time and a little on "chemicals" if I need to instead of buying new hardware, it'll be fine I think. Furd, these are some pretty hefty eyes on the end of the turnbuckle, not that easy for me to just "open", in the field anyway.
So, anyway, using the torch worked out, loosened it up so I could turn it and get'er unscrewed.
The mention in post #5 of using some synthetic grease, well I happen to have some of this: Super Lube Synthetic Grease with Syncolon Multi Purpose Lubricant 3 oz - Amazon.com
So what would I do, mix that with some phosphoric acid and maybe some dish soap? Then smear it on the turnbuckle, and let it penetrate a while like penetrating oil? I do have a jug of some of the metal prep phos-pho stuff that Gunguy45 mentioned too.

 

Eh, once they're loosened up, there's no need to use fancy acid/grease/soap trick.
Just soak them in penetrating oil (or acid) for a while.

Grab a wire brush and clean the surface rust off the screw end,
grab a battery cleaner and clean out whatever rust you can reach from the interior bolt end.

Once both are brushed clean, soak them, brush clean, and re-assemble.