Wash your gate half yearly, this must be done with a high pressure cleaner, after you have sprayed it, use sopa and warm water and give the whole gate a wipe down, then wash off with a hospeipe.
Cleaning up dirt is not the only issue you need to check up on, animlas inside your automatic gate machine could cause some large issues, snail and slugs can cause ithe slime to become highly conductive and even a tiny amount of moisture. If spider webs build up with moisture, this can also be a very good conduct for electricity and damage your gate.
There are certain parts of your gate that will always need lubricating, this will need to happen fairly regularly, the bearing hinges and and wheels will need to be lubricated if they are not covered properly. There is also the bearings that need to stay lubricated. Some swing gates have an internal chain that need lubrication.
For more information contact a proffesional in your area.