I have done three driveshafts with good results.
I have also done steering gear in a wall paper hanging bucket.
I have basically done three car restorations using this stuff, and some spot work on other cars. What I have found is that if you leave zinc coated parts in ER too long it will pull the zinc off the part. It will also remove paint from parts. This is usually not as big of a problem as the zinc lifting. When you reuse it the color turns black and will leave a residue on parts but it can removed with water and light scrubbing. But when you do that make sure you dunk the part in fresh ER otherwise it will flash rust quickly. I really like to dunk the just treated part in fresh ER and let it dry to protect it further.

Agree

I’ve noted when using it in winter that the results depend a lot on temperature. I’ve heard of some folk using an aquarium heater to speed up the process, but haven’t tried it myself yet.

Agree as once it’s used a few times it looses its effectiveness and when doing larger parts new or lightly used worked best and eliminated the black coloration you mentioned. For protection I’ve had excellent results using Resto Guard Dry, a spray on and it dries leaving part natural looking, and Rust Prevention Magic, where you heat the part and brush on a wax like product that melts shiny on parts but once part cools it’s not visible.

It works better if agitated or using a small pump... even if not spraying directly on the part and allowing to run off, just agitation makes it work quicker.
Also you can buy a CHEAP aquarium heater to make it work faster in the winter.

How is everyone treating parts after removing them from Evapo Rust to keep them from flash rusting? I read that dipping it in fresh ER is good, but not sure I understand that.

T-9 Boashield is what I use

-Get a tube section wide enough to barely fit the driveshaft.

-Buy some plastic adhesive that is designed for that type of pipe and glue one end permanently so it won't leak. It is usually in the same aisle as the pipe at Home Depot.

-This Cuda driveshaft only needed one gallon to full submerge.

-Remember that most driveshafts float since they are welded tubes so you might want to throw the yoke on top like I did, to weigh it down.

-Also buy a cheap aquarium pond heater. The warmer the fluid the more effective it is. 85 degrees is a great temp. If it is cold in your garage it works real slow.

-Pull the object out each day to scrub any residue off so the fluid can attack a new layer.

-Markings such as on driveshafts may disappear if the paint is water based or latex. Or if the paint is on a rusty portion of the object. I had to dip test a GM driveshaft to make sure the fluid level in the pipe was just below the stripes, otherwise they would have been destroyed. They used a really crappy paint to make those ID stripes.

BEWARE USING IT ON POTMETAL ITEMS - THEY CAN DISSOLVE! I really messed up a steering column component that way.

Evaporust recently came out with a gel version for this application.

https://www.homedepot.com/p/Evapo-Ru...E&gclsrc=aw.ds

That looks very similar to Bilt-Hamber Deox Gel, which has been around for a few years, although pricey down here. Works well if you cover it with cling wrap to slow the drying.
Hopefully the Evaporust gel will be available down here soon.