Proper cleaning and degreasing of copper tubes is essential before brazing, welding, or putting them into critical service. Contamination from manufacturing oils, drawing compounds, storage corrosion, and handling can compromise joint integrity, degrade process fluids, or cause failures in oxygen, refrigeration, and medical gas systems.

CoreMetal Steel supplies copper tubes with factory cleaning options for critical service applications worldwide.

Types of Contamination

• Manufacturing oils: Drawing compounds, swaging oils, and cutting fluids
• Storage films: Oxidation and tarnish from atmospheric exposure
• Handling contamination: Fingerprints, glove residues, workshop dust
• Installation debris: Metal chips, solder dross, pipe-cutting compound

Solvent Cleaning (Degreasing)

Solvent Selection

• Acetone: Fast-evaporating, excellent degreasing. Flammable.
• MEK: Strong solvent for heavy oils and waxes
• IPA: Moderate degreasing, safer handling
• Proprietary blends: Engineered for specific contamination types

Procedure

1. Wipe exterior with lint-free cloth moistened with solvent
2. For interior, pull solvent-soaked swab through tube
3. Allow complete evaporation (minimum 5 minutes)
4. Repeat if contamination persists
5. Store cleaned tubes in sealed plastic bags

Alkaline Cleaning

For heavy oil and grease contamination, alkaline solutions provide thorough cleaning:

• Sodium hydroxide (NaOH): 50-100 g/L at 60-80C for 10-30 minutes
• Proprietary alkaline cleaners: Follow manufacturer specifications
• Must be followed by thorough water rinsing and drying
• pH of rinse water should be neutral (6.5-7.5)

Acid Pickling

Removes oxide films and light scale:

• Dilute sulfuric acid (H2SO4): 10-20% at 40-60C
• Dilute hydrochloric acid (HCl): 5-10% at ambient temperature
• Typical immersion: 1-5 minutes
• Must be followed by copious water rinsing and immediate drying

Special Service Requirements

Oxygen Service (ASTM G93)

Oxygen systems demand extreme cleanliness because oil residues can ignite explosively in oxygen-rich environments:

• Solvent clean, then alkaline clean, then rinse with high-purity water
• Verify cleanliness with UV fluorescence test (less than 500 mg/m2 residue)
• Cleaned components must be sealed immediately with oxygen-compatible caps
• Workers must use oxygen-clean gloves during handling

Refrigeration Service (ASHRAE/ARI Standards)

Refrigeration copper must be free of moisture and oil to prevent compressor damage:

• Factory-cleaned tubes are sealed with nitrogen charge and plastic end caps
• Verify internal cleanliness by solvent flush and residue weighing
• Maximum allowable residue: typically 0.038 g/m2 (3.8 mg/ft2)
• Moisture content must be below 20 ppm

Medical Gas Service (NFPA 99)

Medical gas piping requires the highest cleanliness standards:

• Cleaning must comply with NFPA 99 and CGA G-4
• Factory cleaning with special degreasing agents verified by testing
• Each tube must be individually sealed with end caps
• Cleanliness certificate required for each lot

Cleaning Verification Methods

Water Break Test

Clean copper surfaces are hydrophilic. Spray clean water on the surface – if the water forms a continuous film for at least 30 seconds, the surface is free of oils.

UV Fluorescence Test

Many oils fluoresce under ultraviolet light. Inspect the cleaned surface under UV light at 365 nm. Acceptable if no fluorescence is detected.

Gravimetric Analysis

Rinse with solvent, evaporate the solvent, and weigh the residue. Compare against allowable limits for the specific service.

Best Practices

• Clean tubes immediately before brazing or assembly, not weeks in advance
• Use clean, lint-free cloths – never shop rags
• Handle cleaned tubes with powder-free gloves only
• Store cleaned tubes in sealed polyethylene bags with desiccant
• Label cleaned tubes with date and cleaner identification
• Re-clean any tube that has been open to atmosphere for more than 24 hours

Why Choose CoreMetal Steel

CoreMetal Steel supplies copper tubes with factory cleaning and sealing for critical service including oxygen (ASTM G93), refrigeration (ASHRAE), and medical gas (NFPA 99) applications. All tubes are individually sealed, tested, and certified.

Contact CoreMetal Steel today for copper tube cleaning and supply for your critical service application.