Stand outside and look at the gate after a full night of fog, then check the notes at steel gate fabrication carlsbad preflight sim for the order they list these problems in. A metal gate in Carlsbad, CA sits in a salt air path that runs from the Pacific up past Agua Hedionda Lagoon and Batiquitos Lagoon, and the marine layer in San Diego County keeps that steel damp past sunrise. The same moisture sits longer in sheltered spots, so rust shows up first where the salt never gets rinsed off.
The gate steel stays wet longest where it cannot shed water. Sheltered parts of a coastal installation, like the underside of a rail or the inside of a hinge barrel, never see a full rain rinse, and salt just builds up there until the coating starts to lift. Gaps between overlapping plates and stitch welded joints trap water and salt against the tubing, which is where crevice corrosion starts and then bleeds rust streaks down the frame. Hollow picket and rail sections that are sealed at both ends collect condensation inside and rot from the inside out, especially on dual swing and single swing gates left outside without drainage.
A swing gate starts dragging when the frame racks out of square or the hinge post leans, and that sag travels fast down Interstate 5 into Oceanside and Encinitas where soil settles. A compression brace from the bottom of the hinge side up to the top of the latch side straightens the frame, while a tension rod or cable run the opposite way locks it so it stays square. Wrought iron and aluminum behave different here, but both sag the same way when the geometry breaks, and both rust or corrode faster when water sits.
Hinges are the other failure point. A worn hinge pin or dry bearing lets the whole leaf drop a half inch over a year, which throws the latch out of alignment and makes the bottom rail drag on the driveway. Powder coat hides this until the gate starts binding, but the movement is there and it is mechanical, not magic. The fix is pin clearance, packing, and a fresh grease fitting, not a heavier operator trying to muscle a drooping leaf.
The simple truth is water and salt, held in place by poor drainage and sheltered geometry. Galvanized coating helps, but it will not save a sealed tube with no weep hole. Fresh water rinse from time to time removes the salt that holds moisture, and that alone stops most of the bleeding streaks before they start. The gate closer or swing operator only amplifies a problem that began with water sitting too long in the wrong spot.
