Steve Morris from Rock Hardware talks about looking after your screw gates.
I am often asked if you can clean karabiners and if so, is there a safe method? My standard reply is rather conservative. Clean as little as possible and only when absolutely necessary. This basic principle applies to any climbing gear, including ropes and harnesses.
It is easy to use too much lubrication, which attracts dirt and may contaminate nylon slings. Petroleum based lubricants are to be avoided at all costs. Lubricants of choice are WD40, which is fish oil based, or Inox. Remember to use them sparingly, only the smallest amount is required.
Squirting toothpaste into the hinge of a sticking gate aluminium karabiner and working it back and forth can help remove corrosion products and also lubricate the hinge area. Ensure that all the toothpaste is washed out with water.
Simply lubricating aluminium karabiners will not repair mechanical damage; however, it can help with corrosion. Aluminium corrosion products tend to be very bulky (chlorides, carbonates, oxides etc) and so all lubrication with an oil does is make the bulky corrosion product sticky. It needs to be removed as suggested above.
Steel karabiners are a totally different matter and a light lubrication is often all that is required. Always thoroughly air dry your karabiners after washing or the spring will corrode. The less that is done the better.
(NB. Thank you to Philip Toomer for teaching me this method)