My new son-in-law is an over-the-road truck driver and he seems to have an almost unlimited supply of 4 x 4 posts that they use under loads such as pallets, etc. They appear to be mostly oak and pine and are different lengths, but most pretty long. Husband (who is usually always negative about anything around the homestead) says they will rot if I just use them as fence posts. Is there something I can dip them in to keep them from rotting as fast???? If so, what is it called and where do I buy it??? thanks!