Practical Methods for Rust Removal and Long-term Anti-rust Treatment of Plastic Molds

Rust formation often occurs on mold surfaces due to high workshop humidity or cooling water leakage during mold storage. Rust will scratch the mold cavity surface, bring defects to molded plastic parts and shorten mold service life. Proper rust removal operation together with matched long-term anti-rust schemes can protect forming surfaces, preserve mold precision and support stable production.

Rust Grade Judgment and Pre-operation Preparation

Before rust removal work, judge the corrosion level and distinguish surface rust, moderate rust and deep rust. Surface rust only exists on the outer layer of steel and mostly appears on non-forming mold surfaces. Moderate rust creates tiny rust pits and slightly affects forming surfaces. Deep rust forms obvious depressions and imposes influence on mold dimensions. Keep the working environment dry and ventilated. Shield mold circuits and cooling connectors to prevent rust remover splashing into water channels and ejector mechanisms. Record the position of inserts and ejector pins before disassembly to facilitate subsequent assembly and resetting. Soft tools are adopted for forming surfaces to reduce surface scratches.

Rust Removal Operation for Light Surface Rust

Surface rust can be wiped with anhydrous alcohol or dedicated mold rust remover, non-woven cloth and copper brush. Steel wool and other high-hardness tools cannot be used, or scratches will be left on the cavity. Wipe along the polishing texture. After wiping, clean residual agent with new non-woven fabric and confirm rust traces are cleared. For textured surfaces, apply diluted neutral rust remover. Clean quickly after short contact to avoid agent damage to original texture. Leave the mold to dry fully after treatment and confirm no moisture residue on the surface.

Treatment for Moderate and Deep Rust

For moderately corroded areas with rust pits, use fine oil stone together with anti-rust oil for polishing to remove rust layer gradually. Maintain even polishing force and control steel removal volume so as not to change molding dimensions of plastic products. Mirror forming surfaces need re-polishing to restore surface smoothness after grinding. Deep rust with relatively deep pits can be repaired by mold welding before grinding and polishing. Welding materials should match mold base steel to lower stress risks. Test cavity dimensions after treatment to ensure dimension changes stay within allowable ranges.

Key Points for Mold Cleaning and Moisture Drying

After rust removal, fully clean the whole mold to wipe off rust powder and residual agent. Flush cooling water channels separately and blow residual water inside pipelines, since residual water in channels is a major inducement of rust during storage. Compressed air can blow debris in mold insert gaps, ejector pin holes and exhaust slots. The compressed air system is recommended to install drying equipment to reduce water vapor adhesion on steel. Leave all mold components to stand for enough time and confirm no hidden moisture in gaps.

Short-term Anti-rust Scheme During Production Intervals

For short protection when mold stops production for one or two days, coat thin layer of mold anti-rust oil evenly on forming surfaces, and add lubricating grease on sliding parts including ejector pins and guide posts. Confirm clean parting surface before mold closing. Store closed mold on dry workbench. Keep workshop humidity in reasonable range and inspect surface status regularly. Wipe off water vapor timely once found.

Long-term Anti-rust Treatment for Mold Storage

Before long-term mold sealing storage, clear all plastic scraps and check exhaust slots and insert gaps. Spray hard-film anti-rust agent on forming surfaces and add lubricating grease on sliding components. Blow cooling water channels dry and fill anti-rust water agent to protect pipelines. Wrap outer mold with anti-rust film and place desiccants inside. Store mold on constant-temperature dry mold shelf. Open package for regular inspection during storage, observe anti-rust coating status and supplement anti-rust materials as required.

Daily Prevention Management Skills

Control workshop ambient humidity to reduce condensate generation. Close cooling water timely after production to avoid condensate caused by temperature difference. Clear plastic scraps and check water stains on mold surface after mold use. Reduce direct hand contact with forming surfaces during mold maintenance and trial molding, because sweat from human hands easily triggers rusting. Different steel grades vary in anti-corrosion performance. Stainless mold steel such as S136 has lower rust risk, while ordinary pre-hardened steel requires higher inspection frequency and early anti-rust maintenance.