4831 a little clumpy

[fishdoggydog]

Two years ago I opened up a metal can of 4831 that I had for years, it had rust in it and I tossed the half can of powder in the trash. The new can of 4831 I bought to replace it was plastic, last time I opened it was the first time, and that was about a year ago. Now the powder is coming out clumpy, like it has taken on moisture. I know the basement is the wrong place to have been storing my supplies, but it is what it is, so what do you think, this powder OK to use?