So we were contacted by a company that sells cleaning equipment. One of their clients has had the brush housing in these small sweepers rot away. So they asked us what we could do about it.
First we used sealants in the front chemical and motor housing.
Then we used a heavy duty urethane coating for the brush housing. So far the machine is holding up quite well. It is used by the NJ Turnpike to clean between toll booths.