Metal window frames are often easy care but occasionally rust takes a hold. Rust can occur on other types of frames as well. Dealt with quickly, rust is not a problem at all.
Step 1 - Examine the Rust Spots
If rust appears on your window frames you need to check carefully to see how serious the problem is. Some rust spots can look alarming but if they are caught in time, will simply scrub away with a dry cloth or by using any of these rust removers. Superficial rust is created when water remains in contact with metal for a length of time but then dries off. The oxidation process has started but is not established in the metal surface.
Step 2 - More Severe Rust Spots
If the rust spots will not respond to a dry cloth you need to resort to something more effective. Damp emery cloth will remove rust that has become established and clean down to fresh metal. The new fresh metal will be pitted where the rust has destroyed the surface.
Step 3 - Aluminum Frames
Aluminum frames can suffer a surface attack very similar to rust in iron and steel. This attack is also caused by extended contact with water.
Step 4 - A Very Simple Cure
Caught early, most of the rust spots on aluminum frames can be removed by the application of a balled up piece of aluminum foil. Simply scrub the rust spot with the foil and it will vanish. This method will work very well even on established rust areas.
Step 5 - Wire Wool
If the aluminum foil does not work use a pad of wire wool to scrub the rust spot away. Keep the wire wool from scratching any surface that might be adjacent to the rust spot. Because the wire wool is stronger than the aluminum you need to be careful to clean up afterwards. It is possible for stray fibers of the wire wool to be driven into the surface of the aluminum and create a second rust possibility.
Step 6 - Established Rust
Rust that has been eating at a metal window frame for some time will have become established. The effect of the rust on the metal will be to break down the surface so that it breaks off in flakes. This rust needs to be cleared as much as possible with a wire brush. Once the bulk of the rust is removed a commercial rust remover is required. Rust remover can be applied to metal frames with a paint brush. Most removers need to be applied and then brushed off when they dry
Step 7 - Prevention
Although it is relatively easy to remove most minor rust damage it is far more important to prevent the rust starting in the first place. Ignored, rust can cause significant damage to metal window frames. Since the rust is caused by contact with water, simply preventing that contact will prevent the rust.
Once you have cleaned off the rust from your metal frames you need to paint them or coat them with a water repellent surface like grease.