Aluminum plants manufacture a grade of aluminum called 6061-T6. It is solid aluminum and is made to withstand the harsh elements of a marine environment. It doesn't rust and, if taken care of properly, could last for decades. The cost of the aluminum as opposed to the galvanized is more expensive, but it is a good investment because the aluminum will last much longer. Hot dipped galvanized steel is a fabricated, raw steel dipped in zinc galvanizing. Unfortunately, over time, the galvanized coating will wear down and the exposed steel will rust the boatlift. This is especially true in lifts installed in salt water.