Although steel sectional garage doors mostly have a 1 year guarantee from its manufacturers, it is best to still clean and maintain your garage door.
You can wash your garage door by using mild soap along with a soft vehicle brush. The more you wash and clean your garage door, you will lessen the built-up of the harsh elements and filth that can damage your door.
For the customers who live in coastal areas, where blowing winds and industrial areas are close by with sea salt and other elements of factories, there are more corrosives in the area and cleaning it more regularly will improve the condition of your door and decreases the chances of damage to the steel and other parts of your system.
It is important to stay away from aggressive cleaners or compounds on or around your garage door.
For any other damages to the steel, that you could not maintain with regular cleaning; contact a trained service technician.