WD-40 is designed to prevent rusting by displacing water in cracks and crevices in metal (that's what the "WD" stands for). It's also a versatile lubricant and can even be used as a solvent, but there are some places you should never spray it.
16 Uses for WD-40 Everyone Should Know About
WD-40 doesn’t have the same viscosity as traditional grease or oil, and it can damage certain finishes and cause problems if used as a replacement. While it’s tempting to think that it’s a good idea anywhere you need to reduce friction, here are some places you should absolutely never use WD-40.
When you need to lubricate a hinge on a pair of sunglasses or remove a price tag from a plastic wrapper, you might reach for a can of WD-40. However, you should never use it on a clear plastic surface or on polystyrene or polycarbonate.
Products containing styrene are often labeled #6 and include things like toys, disposable cups and cutlery, and appliances like smoke detectors. Polycarbonate, also known as #7, is found in kitchen appliances like refrigerators, clear containers, plastic lenses, and safety gear. Due to the chemical makeup of WD-40, it can damage these plastics and ruin things like sunglasses with plastic lenses. When in doubt, avoid using WD-40 on plastic.
