Of course. The impregnation process must not contain chromium or arsenic, but copper that is a common reagent in green colored impregnation, is allowed. In fact, it’s not advised to manufacture equipment that will be exposed to the elements year-round from non-impregnated timber.
Some will speak about so-called “hard-wood” equipment that are sometimes marketed as non-rotting. This is false, as non-rotting timber doesn’t exist. The only way to prevent rot is to use specialized chemicals design to prevent rot-fungus from eating it.