I've never pumped inert gas into any partial container of epoxy or hardener. They've lasted years after being opened, anyway. Resin doesn't oxidize, but the hardener does. However, when it does the only result is a color and smell change. The hardener gets darker and acquires a smell like a diaper pail. It still cures fine with no loss of strength. The big problem would be if you want a clear epoxy finish.

Note that the amount of oxidation depends on the brand of epoxy. Modern high modulus low viscosity epoxies like MAS and System Three SilverTip oxidize very slowly and will not change colors even after years of sitting in aclosed previously opened jug.

The main thing I worry about is making sure that the epoxy doesn't freeze, otherwise the resin will crystallize. That's easy enough to fix by soaking ing a hot (140 degree F) water bath, but it means that you can't just take advantage of a sudden warm spell during winter.

Pumps. I just make a point of buying new pumps every year. They're so cheap that even if you count your time at minimum wage it's not really worth the trouble to clean them. But if you must, yes, vinegar will break down and neutralize hardener. The problem with that is contaminating the rest of the jug.

Resin and hardener, when confined in small spaces will get sticky and cause the pump mechanism to clog and stick. What I've had good success with after a winter of not using the pumps is:

1. Resin pumps - wipe the crust off the spout and put into a ziploc or other watertight plastic bag and soak in a hot water bath to dissolve any crystals. Once that's done, return the pump to the jug and pump resin into a clean container until the pump moves freely and delivers a clean stream with no sputtering or bubbles. Then pour the resin from the clean container back into the jug.

2. Hardener pumps - same, except for no water bath.

In both cases it's using the epoxy itself as the pump cleaning fluid. This avoids contamination by any solvents. The downside is that it's a messy process, it unavoidably consumes some epoxy and if the container is not perfectly clean you can contaminate what's left in the jug. That's why I just buy fresh pumps.

Have fun,

Laszlo

Good feedback Laszlo, thanks.

I suppose I should have checked whether pumps are back in supply channels now?

Weeks ago every source I looked at had 'em backordered, which prompted my question about storage, if it should come to that.

   @spclark - I was able to buy MAS pumps from Seattle Marine and Fishing Supply (internet order).   I did that when CLC said they weren't shipping pumps but when I ordered my epoxy kits from CLC just a few weeks ago, they *did* come with pumps.
 

Yah MD, thanks for that!

After reading Laszlo's post I noticed CLC says they have pumps on hand. The shortage was months ago when hand sanitizer outfits were taking all the pumps they could get. Seems that's been resolved, stuff's everywhere now. Epoxy users can relax a bit.