Hidden Signs of Corrosion & Rust in Plastic Injection Molding
— Slide Products
Injection mold cavities are one of the most valuable and expensive assets for plastic molding. However, many technicians underestimate the damage that rust and corrosion can cause until it impacts part quality, increases cycle times and reduces production efficiency.
Signs of Rust in Injection Molds
Discoloration and Ghosting
Early signals of oxidation often present as slight color variations or a dull sheen on part surfaces. Inspect finished products under proper lighting and look for any indicators of inconsistencies in appearance or finish.
Pitting and Surface Defects
Corrosion typically starts as irregularities on the mold itself. Over time, these expand and transfer directly to parts. Examine for small dimples, rough textures or uneven spots, which are often caused by internal pitting.
Increased Friction and Ejection Issues
Rust creates a rough surface which intensifies friction. As a result, components become harder to eject, cycles times increase and parts may get damaged during ejection. Pay attention to heightened resistance, sticking and other unusual defects.
Cooling Inefficiencies and Waterline Buildup
When mold temperatures drop below the dew point during cooling, moisture can form inside the mold. This trapped wetness creates ideal conditions for rust and mineral buildup, restricting water flow over time.
Unusual Odors During Production
Rust produces a sulfuric like or metallic smell when the mold is heated or opened – often indicating that oxidation is occurring.
Flash and Parting Line Defects
Corrosion and uneven areas near the parting line prevent a proper seal. Molten plastic can then escape the cavity, resulting in flashing or gaps in the completed piece. Inspect finished products for excess residue around joints, openings along edges and inconsistent sealing.
