Shelf life of hardener

I read on this forum a few weeks ago that putting it in the fridge would extend the shelf life after opening so that is what I did.

My question is; How do I tell if this hardener is still any good? What does it do when it goes bad? If it is still a liquid is it still good?

I am thinking that hardener goes bad by getting hard in the can after opening. But it may be that the chemical reaction does not work as well after being exposed to air for so long.

For the cost of it I would rather buy some new than ruin my paint job but I am trying to paint pieces parts and it is sometimes a while before I can get back to do another piece.

Thanks for your advise.
John

Well, the safe and conservative approach would be to use it up within the 14 days or chuck it. It's always an issue with those of us who do things piecemeal at diffferent times over a long period. The stuff is reasonably expensive so I find it hard to just throw it away. I have used the OMNI MH168 hardener that had been opened and partially used up two years previously and did not have a problem. I am advised that as long as it is not "lumpy" or "cloudy" or other such obvious abnormality that it is probably alright but that is only hearsay from net talk. I can only verify that some small parts I painted last Spring using 2 year old MH168 turned out just fine. You'll have to make the cost/benefit judgment call yourself.

Rod

I don't think you would want to use a typical MIG shielding gas - at least that used for steel. That would commonly be a 75/25 mix of argon and CO2 or even straight CO2. It's probably better than just air but my guess is that a fully inert gas would be best, such as straight argon that is generally used in the TIG process, although it is also used in MIG welding of aluminum. I have never tried using argon but will the next time I open a fresh can of hardener. BTW I have some Picklex 20 on order that I will be trying out. I am planning on sandblasting some parts in a blast cabinet this winter but will not be able to prime or paint until warm weather in the Spring. It would appear that Picklex 20 would be the ideal product to use in such a situation.

Is this something new from DuPont? Their 8105S urethane activator for Centari AE has no indication on the label that I can see. The can I have is about 3 years old so that maybe the reason. There is no indication that the contents should be used within 14 days of first opening and nothing mentioned about any 6 month limit on warranty of "unopened" cans. The only caution that I can find along those lines is that it says to "Keep container of 8105S tightly closed." There is also no indication of time dependent usage constraints in the tech sheet for the Centari Ultra mix that uses that particular activator. How can a part time purchaser of such products tell when any 6 month warranty begins and ends? Are there now date stamps or serial number indicators on the can labels? In my neck of the woods a can of 8105S could very well sit on a retailers shelf for 6 months :o). I realize that DuPont warranties may not apply to DIY users (e.g. "not for use by the general public" labeling) that are not trained and "certified" by DuPont but I am curious as to how things are tracked in the pro shops regarding such time windows.

Rod