With the onset of winter weather we are often asked about frozen locks. The locks most susceptible to this issue are mailbox locks, automotive locks and padlocks. What is happening when your lock becomes frozen is this: moisture that has been allowed to build up in the lock freezes and the lock plug and its related components stop operating leaving you stuck.
The best way to deal with this issue is maintenance. A lock that has been properly lubricated has no moisture in it and consequently cannot freeze up. A high quality lubricant such as Tri-Flow used periodically will drive the moisture out and ensure consistent operation of your lock year round. Graphite is not recommended. WD40 is a very poor lubricant.
If you encounter a frozen lock cylinder you need to gently heat the cylinder to thaw the frozen water that is trapped inside. The best way is to heat the tip of the key with a match or a lighter and insert the key into the cylinder. Allow the heat from the key to transfer to the cylinder. Repeat this procedure while gently moving the key to the left and/or right until it begins to function again. Depending on the temperature, weather conditions and the amount of moisture in the lock, this will take several matches. The large wooden kitchen matches work the best. Becoming impatient and forcing the issue will result in a broken key and give you a new problem to deal with.
Some people don’t like the slow, gentle approach to thawing out the lock and resort to more drastic measures. This is unwise. Some have taken a torch to the lock to speed things up and have discovered the die-cast zinc cylinders have a very low melting temperature and are quickly destroyed. A heat gun is also not recommended. A hair dryer is safe but not as effective because the heat gets into the inside of the cylinder very slowly. The metal to metal contact of the heated key to the frozen cylinder is still the best approach.
When you get the cylinder operational again be sure to lubricate it to avoid this problem in the future. The lubrication may not be totally effective until the temperatures rise above freezing.