Using old hardener

[Gary]

I have read in many places that hardener goes bad. I was playing around with one of my paint guns so I used some old paint and hardener I had kicking around (over a year old). It seemed to work fine, I was wondering what happens when hardener goes bad ? Also, how long is to long to keep it around.

Thanks Gary

[88GT]

the hardner I use will get chunky when it goes bad.

[Len]

Hardener ages more quickly when there is more air in the container and/or the temperature is higher. So if there's only a little removed from the container it could last longer. You can greatly extend the life of the hardener if you use a little Bloxygen before you put it on the shelf.

Bloxygen Link

[Dennis N. Schmidt]

The simple answer is that for isocyanate based hardeners it hardens. You end up with solid hardener which as you might imagine is rather hard to pour.

Whenever in doubt mix up a small batch with it's appropriate resin (in the case of clearcoat that would be clearcoat) and in a day or two you should have a hockey puck of clearcoat in the mixing cup. If you do the hardener is good. If it's still a liquid it's bad. But normally when it's bad it simply does this hockey puck thing by itself in the can without the resin.

[Gary]

Thanks Guys, Just want to make sure I am not fooling myself and end up with a mess. Wouldn't be the first time

[Joseph]

I had the same question about some hardener for PPG epoxy (DP402LF). I had it sitting around for seven years with only a little used out of the can. I opened it the other day and poured it into a clear container. It was a much darker color than brand new hardener but it had no chunks or crap in it. I wound up using new anyway, but I wonder aboiut the old stuff. I wonder why it got so dark. I guess a test would have told me whether it was good or not.

[Len]

I had the same question about some hardener for PPG epoxy (DP402LF). I had it sitting around for seven years with only a little used out of the can. I opened it the other day and poured it into a clear container. It was a much darker color than brand new hardener but it had no chunks or crap in it. I wound up using new anyway, but I wonder aboiut the old stuff. I wonder why it got so dark. I guess a test would have told me whether it was good or not.

Some additives for "direct-to-metal" primers are not hardeners but are what is called "activator". It may not actually harden the material but instead make it bond to the surface. The main additive for single stage paint and for clear is hardener as is the additive for filler primers but some primers use the word activator to tell you that it's not necessarily a hardener. Old activator may still negatively effect the outcome so you may want to do a little testing before you use it on anything important.

[tbm3fan]

Same here I have a never opened can of DP40 from 1990 and a unopened can of catalyst. Keep thinking I should try them out for the heck of it one of these days and see what happens. This DP40 is back in the days when the PPG epoxy primer had all the bad stuff in it that it doesn't have today such as chromates.

[Joseph]

Was it here that I read you could shoot a little argon/CO2 from your MIG into the container and it would have the same effect as Bloxygen?

[Len]

Was it here that I read you could shoot a little argon/CO2 from your MIG into the container and it would have the same effect as Bloxygen?

That's exactly right but it's a lot handier to have it on the paint bench than in the welder's tank.