How to Repair Hot Runner Corrosion Failure

The repair method for hot runner corrosion failure needs to be selected comprehensively based on the type, degree, and location of corrosion. The core principle is: minor localized corrosion can be repaired by grinding and coating; severe corrosion or structural damage requires replacement of the component. For chemical corrosion (such as pitting corrosion caused by HF), [further treatment is recommended].

I. Repair of Chemical Corrosion (Applicable to pitting and uniform corrosion caused by HF in PFA/PTFE processing)

1. Slight Corrosion (Pit depth < 0.1mm)

Process:

Disassemble affected components (e.g., nozzles, valve needles)

Use silicon carbide sandpaper (800#→2000#) to progressively polish the corroded area, removing oxide layers and fluoride residues

Ultrasonic cleaning (isopropanol + deionized water) to remove particles

Reapply ceramic coating or electroless nickel-phosphorus (Ni-P) plating for surface protection

Applicable Scenarios: Slight grayish-white deposits or shallow pitting near the gate

Advantages: Low cost, short cycle time, can restore more than 90% of original performance

Limitations: Not suitable for areas with damaged structural strength

2. Severe Corrosion (Pit depth ≥ 0.1mm or reduced flow channel diameter > (0.15mm)

Recommended Treatment:

Replace key components such as nozzles and flow dividers directly.

For customized non-standard parts, consider laser cladding repair (e.g., Stellite 6 alloy), followed by precision machining to original dimensions.

Subsequent Protection: Replaced parts should undergo pre-treatment with a ceramic coating.

Optimize process parameters, controlling the temperature ≤350℃ to reduce HF generation.

Data Support: Experiments show that a 0.2mm reduction in the flow channel inner diameter can lead to an 18% increase in filling pressure, significantly affecting molding stability.

II. Repair of Electrochemical Corrosion (Applicable to localized deep pits and crevice corrosion in cooling water systems and dissimilar metal contact areas)

1. Localized Rust and Perforation (e.g., green rust and water seepage at copper-steel joints)

Treatment Process:

1. Cut off cooling water and thoroughly dry the corroded area.

2. Remove rust layer using a steel brush and a weak acid cleaner (e.g., citric acid solution).

3. Repair the corrosion pits using argon arc welding or cold welding (e.g., WEWELDING 80 nickel-based welding rods).

4. Grind smooth after welding and re-insulate (e.g., spray epoxy resin or install PTFE gaskets).

Key Improvements:

Replace the original copper cooling pipe with a stainless steel corrugated pipe.

5. Install ceramic insulating sleeves at different metal connections.

On-site Recommendation: Perform a water pressure test (1.5 times the working pressure) after repair to ensure no leakage.

2. Structural Weakness Caused by Crevice Corrosion

Remedial Recommendations:

Disassemble the insert and clean the corrosion products from the crevice.

Use penetrant testing (PT) to confirm the presence of microcracks.

If crack propagation is found, it is recommended to replace the entire insert.

When reassembling, use the same material (e.g., H13 steel with H13 inserts) and apply thermally conductive insulating adhesive.

III. Verification and Reuse Standards after Repair

Engineering Motto: "Small corrosion can be repaired, large corrosion must be replaced; electrical corrosion must be broken, insulation is the priority."