Staining/painting a compost bin?

Hi all,

I'm building a compost bin at the moment using some Douglas Fir lumber with cedar posts in the corners and ½" hardware cloth. Before I finish installing it, are there any paints or stains that would be safe to use to help it last a little longer? I don't want anything hazardous leaching in to the compost, but would like to keep the bin looking as nice as a compost bin can.

Thanks!