How can you keep cnc router metal parts rust free
Coolant
Machine manufacturers recommend a specific coolant. Metalworking fluid, or coolant, is a chemical formulated to lubricate the cutting tool and act as a rust preventive. Follow the manufacturer's recommendations to avoid rust formation on metal parts exposed to coolant. Never use plain water as coolant; this will cause permanent damage to the machine.
Shavings
Shavings build up in crevices of the machine. Metal shavings collect in all areas inside the machine enclosure and, if ignored, can hold moisture and cause rust. Most machines have a conveyor to remove the bulk of these, but care should be taken to clean hard-to-reach places. Even if the shavings are a material that won't rust, they can cause metal parts in the machine to corrode.
Daily Cleaning
Wipe the machine clean often. Mist from coolant and dust from cutting processes settle on all areas of the machine, inside and out. The dirt and grime can build up and damage the finish of painted surfaces and cause bare metal to rust. Use a mild degreaser to clean up after each use of the machine, followed by an application of light rust-preventive oil.