Injection molds are usually made of tool steel. During production and storage, they may come into contact with corrosive gases, water, and other substances that can cause rust. Once a mold becomes rusty, it can affect part quality and create avoidable production problems. In general, there are three main causes of injection mold rust:
- Gas produced by the decomposition of the melt
- Cooling water inside the mold
- Carbides produced during molding
How to Avoid Rust on Injection Molds
1. Do Not Store Molds in a Humid Environment
When storing molds, always choose a dry and well-ventilated place. It is better to keep molds off the ground and place them on shelves or supports, since moisture can accumulate near the floor. Avoid touching the mold surface directly with bare hands, because sweat can also contribute to corrosion. If the mold temperature falls below the dew point, moisture in the air can condense into water droplets on the mold surface. If these droplets are not removed and dried in time, rust can easily form. After cleaning the mold with a mold cleaning agent, any remaining moisture should also be dried immediately.
2. Let the Mold Cool Down Before Spraying Rust Inhibitor
If anti-rust oil is sprayed onto a hot mold, the mold surface may absorb moisture from the anti-rust agent, which can lead to rust instead of preventing it. A better practice is to wait until the mold temperature has cooled down before applying the anti-corrosion product.
3. Spray the Rust Inhibitor Evenly
When using a rust inhibitor, spray it evenly across the mold surface. Try to avoid concentrating the spray in only one area. It is recommended to apply it evenly over the full surface two times or more to make sure there are no missed areas.
4. Use a Long-Term Mold Rust Inhibitor
For molds that are not used frequently or need to be stored for a long time, dry vaporizing rust inhibitors are not the best option. In these cases, it is better to use a conventional oily rust inhibitor and keep the mold properly sealed during storage.