The door looks fine. It has looked fine for eleven years. It is a coated steel door, it gets washed when the car does, and there is not a mark on it from the driveway.
Then one morning it comes down at an angle and jams solid, and the reason is a piece of steel cable the diameter of a pencil lead that nobody has looked at since it was installed.
Coastal air does not corrode a garage door evenly. It concentrates, and knowing the four places it concentrates is most of what a homeowner needs.
Why salt air is different from ordinary damp
Steel rusts when iron, oxygen and water meet. Salt does not participate in that reaction, which is why people are surprised by how much difference it makes. What it does is make the water conductive.
Corrosion is electrochemical. It needs current to flow between anodic and cathodic areas on the metal surface, and in clean water that flow is limited by how poorly the water conducts. Salt turns that thin film of condensation into an electrolyte, and the reaction accelerates sharply.
Chloride does a second thing that matters more for coated steel: it attacks passive layers and gets under coatings at any small defect, so corrosion spreads sideways beneath paint that still looks intact from a foot away.
Add South Florida humidity, which means condensation forms most nights on any surface that cools below the dew point, and you have a wetting cycle nearly every day of the year rather than after rain.
The four places it concentrates
- The bottom six inches of the lift cables. The most important one. The cable terminates at a bracket at the base of the door, which is the lowest point of the whole assembly and the wettest. Water sits there. The floor is wet after every storm. A cable can be bright and clean at eye level and rusted to a fraction of its section in the last six inches.
- The bottom brackets and fixings. Same location, same water. These carry the cable, so their condition is not cosmetic.
- The springs. Spring wire is coated, usually black or galvanised. Salt finds any nick in the coating and works between the coils, where nobody looks and where the metal flexes on every cycle. Corrosion in a spring reduces its effective wire diameter, which reduces its cycle life dramatically.
- The bottom hinges and the end stiles. The lowest section of the door itself, particularly on doors with a steel skin and a foam core, where water that gets in cannot get out.
Notice that all four are in the bottom couple of feet. That is not a coincidence, it is gravity and a wet floor.
The two-minute inspection worth doing twice a year
Open the door fully. This unloads the cables and lets you look at them safely.
Look at the last six inches above each bottom bracket. You are looking for two things: rust that has gone past surface colour into pitting, and strands standing proud of the lay of the cable. A frayed cable looks fuzzy, and once you have seen one you will not mistake it.
Then look along the springs above the opening. Surface discolouration is normal. Orange flaking between the coils is not.
Do not put your hands near the bottom bracket, and never try to move a cable. That bracket is under full spring tension whenever the door is not fully open, and it is where the serious injuries in this trade happen.
What actually helps, and what does not
Rinsing the bottom of the door helps, particularly if you are within a few miles of the water. Salt is soluble; the entire fix is fresh water. Include the bottom brackets and the track ends, not just the panel.
Lubrication helps, because a light film keeps the electrolyte off the metal. Rollers, hinges, end bearings and the spring coils, with a proper garage door lubricant, twice a year.
Galvanised hardware helps and is worth specifying here. It does not make anything immortal, and galvanising is a sacrificial coating with a finite service life in this environment.
Grease on the tracks does not help. It is the most common mistake we find and it makes things worse: grease collects sand, which holds moisture against the track and grinds at the rollers.
Painting over rust does not help. Chloride under the coating keeps working in the dark and you have removed your ability to see it.
The money question
No prices, but the arithmetic on this one is stark and it is worth stating clearly.
A pair of cables is one of the least expensive parts on the door and replacing them on a healthy door is a short visit. Replacing them after one has snapped means re-tracking the door, resetting both cables in the drums, re-tensioning the spring, and dealing with whatever the twist did to the sections.
Same part. Different afternoon, and a different order of magnitude. The whole case for the two-minute inspection is the gap between those two.
What not to buy
- Do not buy one cable. They are the same age and have done the same cycles in the same air.
- Do not buy stainless hardware throughout as a cure. It has its place, it is expensive, and mixing stainless with plain steel fasteners creates a galvanic pair that corrodes faster than either alone. This is a job for someone who knows which parts to change, not a blanket upgrade.
- Do not buy a new door because the hardware corroded. The panels are usually the healthiest part of a coastal door. It is the moving steel that goes.
- Do not accept a cable replacement that leaves the drums and bottom brackets untouched. If the bracket is corroded, the new cable is anchored to a rusted part.
The short version
Salt turns every night’s condensation into an electrolyte, and gravity puts the water where the most important parts are. Look at the bottom six inches of both cables twice a year and rinse the underside of the door with fresh water.
That advice costs nothing and prevents most of the calls we get. We are aware of how that reads on a business website. It is still the correct advice.
M&M Garage Door Service · (954) 787-3756 · mnmgaragedoorrepair.com
Serving Plantation, Fort Lauderdale and Broward County.