What to Do If the Air Compressor Receiver Rusted?

I. Step 1: Shut Down the Machine to Assess Rust Severity and Determine Whether It Can Continue to Be Used

• Mild Rust: Only a small amount of rust spots appear on the outer surface of the tank, without peeling or blistering. There is no obvious rust or water accumulation inside the tank, and the wall thickness has not thinned (measured with a caliper, the deviation from the factory wall thickness is ≤5%). Such rust does not affect structural safety and can be put back into use after rust removal and repainting.
• Moderate Rust: A large area of rust spots appears on the outer surface of the tank, accompanied by peeling and blistering. There is local rust or a small amount of corrosion pits inside the tank, and the wall thickness deviation ranges from 5% to 10%. Professional rust removal and anti-corrosion repair are required. After repair, a hydrostatic test must be performed (the test pressure is 1.25 times the working pressure), and it can be put into use only after passing the test.
• Severe Rust: The tank has large-area corrosion, perforation, or cracks, or the depth of corrosion pits inside the tank exceeds 10% of the wall thickness, with a wall thickness measurement deviation >10%. In such cases, continuing to use is strictly prohibited. The receiver must be scrapped and replaced immediately to avoid safety accidents caused by insufficient structural strength.

II. Graded Treatment: Repair Solutions for Different Rust Severity Levels

1. Mild Rust: External Rust Removal and Repainting + Internal Drying and Cleaning

• External Treatment: Use sandpaper or a wire brush to grind off the rust spots until the metal luster is exposed. After removing surface dust and oil stains, apply two coats of special anti-corrosion paint for air receivers (choose epoxy zinc-rich primer for the undercoat and polyurethane topcoat for the finish, ensuring the coating thickness is ≥80μm).
• Internal Treatment: Open the drain valve and manhole of the air receiver, completely drain the condensed water and impurities inside the tank, and purge the tank with dry compressed air to ensure no residual water is left. If there is a small amount of loose rust inside the tank, wipe it clean with a cloth; no additional painting is required (internal painting is prone to peeling and contamination of compressed air).
• Key Operation: Restore the function of the drain valve after repair to ensure that condensed water can be discharged normally and avoid re-accumulation of moisture.

2. Moderate Rust: Professional Rust Removal + Anti-Corrosion Repair + Hydrostatic Test

• Internal Tank Rust Removal: Professional personnel are required to perform mechanical derusting (such as sandblasting, shot blasting) or chemical derusting (such as pickling and passivation) to completely remove rust, oxide scale, and oil stains inside the tank, ensuring the metal surface cleanliness reaches Sa2.5 level (near-white metal finish).
• Internal Anti-Corrosion: Immediately apply a special food-grade anti-corrosion coating (such as epoxy resin coating) inside the tank after rust removal to avoid secondary rust and prevent coating peeling from contaminating compressed air.
• Hydrostatic Test: After the repair is completed, conduct a hydrostatic test in accordance with national standards. Observe whether the tank is deformed or leaking during the test. Only after passing the test and obtaining a test report can it be put back into use.
• External Repair: Treat external rust simultaneously, following the same repainting process as for mild rust.

3. Severe Rust: Immediately Scrap and Replace with a New Tank

III. Core Prevention Measures: Avoid Air Receiver Rust from the Source

1. Equip with Drying and Filtration Equipment to Reduce Moisture and Oil Content
   • If the downstream process has high requirements for air quality, it is necessary to equip with a refrigerated air dryer (or adsorption air dryer) and three-stage filters to effectively remove moisture and oil from compressed air, reducing corrosion media inside the tank from the source.
   • Even without a refrigerated air dryer, install a pre-filter at the air compressor outlet and ensure the drain valve of the air receiver works normally to avoid long-term accumulation of oil and water inside the tank.
2. Regularly Discharge Condensed Water to Keep the Tank Dry
   • Manual Drainage: Discharge the condensed water in the air receiver at least 1-2 times a day. Increase the drainage frequency in humid areas or rainy seasons to ensure no water accumulates inside the tank.
   • Automatic Drainage: It is recommended to install an automatic drain valve and set a timing or automatic drainage mode to avoid water accumulation caused by manual forgetting. This is the most critical daily operation to prevent rust.
3. Regular Inspection and Maintenance to Handle Small Problems in a Timely Manner
   • Inspect the appearance of the air receiver monthly. If a small amount of rust spots is found, grind and repaint them in a timely manner to prevent rust from expanding.
   • Conduct a comprehensive inspection annually, including wall thickness measurement, hydrostatic test (or air tightness test), and calibration of safety valves and pressure gauges, to ensure the equipment meets safe operation requirements.
   • Keep the air receiver installation environment dry and well-ventilated, and avoid long-term exposure of the tank to humid, dusty, or corrosive gas environments.
4. Standardize Operation to Avoid Overpressure and Overtemperature Operation
   • Operate strictly in accordance with the rated working pressure and temperature of the air receiver. Avoid overpressure and overtemperature, which may cause damage to the anti-corrosion coating or metal fatigue of the tank and accelerate rusting.

Summary