Injection Mold Rust Treatment and Anti-Rust Methods

Injection molds are critical equipment in plastic production. Their precision and surface quality directly determine product performance. Rust is one of the most common defects caused by high humidity, water leakage, poor maintenance, and corrosive materials. Rust not only causes surface defects such as spots, streaks, and dimensional variations but also shortens mold life and increases production costs. This article systematically introduces graded rust removal methods, full-process anti-rust strategies, and key precautions to help manufacturers reduce mold damage and ensure stable production.

I. Graded Rust Treatment for Injection Molds1. Mild Rust (Surface Floating Rust)Mild rust usually appears after short-term exposure to moisture. It only attaches to the surface without pitting. The treatment focuses on physical cleaning to protect the mold base.

First, clean oil and residue with a neutral mold cleaner and non-woven cloth. Then dry the surface completely with a hot air gun. Use 3000-mesh or finer sandpaper to polish the rust gently. Finally, apply a thin layer of anti-rust oil to form a protective film.

2. Moderate Rust (Firm Rust with Minor Pitting)When rust penetrates the surface, a combination of chemical and physical methods is required.After cleaning and drying, apply a neutral rust remover designed for molds and allow it to stand for 5 to 10 minutes. Scrub lightly with a soft brush, then rinse and dry thoroughly. Use polishing paste to restore smoothness and apply anti-rust oil immediately. For internal cooling channels, use a special pipeline rust remover for circulation cleaning.

3. Severe Rust (Deep Rust, Pits, and Large-Area Corrosion)Severe rust usually results from long-term dampness or water leakage and requires professional repair.Remove thick rust layers with 1000–2000 mesh sandpaper, then use a rust remover for deep treatment. For pits, use mold steel welding for non-appearance areas. For mirror surfaces, perform progressive polishing from 2000 to 6000 mesh. Severely corroded cooling channels must be replaced or treated with anti-corrosion coating.

II. Full-Process Anti-Rust Protection1. Daily Anti-Rust During ProductionCheck cooling channels weekly for leaks and scale. Drain and blow dry all water after each shift. Clean the cavity, parting surface, and ejection components before applying a thin anti-rust film. Lubricate guide pins, ejector pins, and sliders with high-temperature grease to isolate moisture.

2. Protection During Shutdown

For short-term shutdown (within 7 days), clean and dry the mold, then spray volatile anti-rust agent. For long-term shutdown (over 7 days), apply heavy anti-rust grease, wrap the entire mold with anti-rust film, and seal all connectors.

3. Storage Environment Control

The storage area must be dry and ventilated, with humidity controlled between 40% and 60%. Use dehumidifiers if necessary. Molds should be placed on shelves, not directly on the ground. Conduct monthly inspections to reapply anti-rust materials when needed.

III. Key PrecautionsNever use strong acids such as hydrochloric or sulfuric acid, as they severely erode mold steel. Complete drying is essential for any rust treatment or anti-rust step. Choose appropriate anti-rust products based on usage duration. For corrosive materials such as PVC, use corrosion-resistant mold steel. Establish a mold maintenance log for traceable management.

SummaryRust treatment follows the principle of graded handling, while anti-rust protection requires full-process control. Scientific rust removal reduces mold damage, and standardized anti-rust measures greatly extend service life. A complete maintenance system improves product quality, reduces downtime, and supports efficient, stable injection production.