Sometimes, when your Heavy Duty enclosure is put in very corrosive environments (Like very close to a Beach) rust may end up building up over time. The housings are Heavy Duty, but an anti-corrosive housing is a different story. With a little work you can help keep rust from building up on your housing in these harsh environments.
First of all, you will most likely want to paint the housing with a rust resistant paint, like Rustoleum products. It is recommended to repaint the housing once every year, to prolong the life of the housing.
Secondly, you may also want to purchase stainless steel latches for your housing. The manufacturer of the heavy duty housings normally doesn't send them with stainless steel latches to try and keep costs relatively low for customers, but you do have the option to purchase those separately if you like. Here's one place to purchase stainless steel latches for the sides of the housing:
http://www.southco.com/products/k2-k3-k4-k5-rotary-draw-latches/k3-1660-52.html
With these suggestions you should be able to significantly extend the life of your housing in corrosive environments.