Fitur	Flensa Baja Tahan Karat	Carbon Steel Flange
Main Alloy Elements	Besi, Kromium (≥10.5%), Nikel	Besi, Karbon (0.2–0.6%)
Ketahanan Korosi	Bagus sekali	Rendah (requires coating or lining)
Appearance	Silvery, bright, non-rusting	Dull gray, prone to rust
Magnetic Property	Usually non-magnetic (austenitik)	Magnetik
Biaya	Lebih tinggi	Lebih rendah
Typical Grades	SS304, SS316, SS321	ASTM A105, A350 LF2, Q235

1. Inspeksi Visual

Flensa baja tahan karat generally have a bright silver finish and resist oxidation. Even after extended exposure to air and moisture, they maintain a clean, shiny surface.

Flensa baja karbon, di sisi lain, often appear dull gray or matte black. Without protective coatings like paint, menggembleng, atau minyak, carbon steel flanges will karat seiring berjalannya waktu.

Visual differences:

• Baja tahan karat: Polished or satin finish, clean look, no surface corrosion

• Baja karbon: Dull, may have red/brown rust spots or black oxide coating

sasa lonjong supplies flanges with mill finish or custom surface treatment to ensure easy identification and superior corrosion protection.

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2. Magnet Test

This is a quick and easy field test to identify the general category of steel:

• Baja karbon is always bersifat magnetis

• Baja tahan karat varies:

  • Austenitic grades (misalnya, SS304, SS316): Non-magnetik or slightly magnetic

  • Ferritic and martensitic grades: Magnetik

Place a magnet on the flange. If it sticks strongly, it’s likely carbon steel or ferritic stainless. If it barely reacts or does not stick, it is likely baja tahan karat austenitik.

Catatan: Cold-working or machining austenitic stainless steel can make it slightly magnetic, so this test is not 100% conclusive.

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3. Spark Test

The spark test is commonly used in metal workshops:

• Baja karbon produces panjang, branching orange sparks when touched with a grinder

• Baja tahan karat produces shorter, fewer sparks that are red or dull orange, often with less branching

This method requires experience and should be done with care. Always follow safety precautions when using grinders or spark tools.

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4. Weight Comparison

Baja tahan karat adalah slightly denser than carbon steel:

• Density of carbon steel: ~7.85 g/cm³

• Density of stainless steel (304/316): ~8.0 g/cm³

Although the difference is small, stainless steel flanges may feel slightly heavier than carbon steel flanges of the same size and design.

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5. Chemical Testing with Spot Kits

For more accuracy, chemical spot test kits are available to detect the presence of nikel, kromium, or molybdenum in stainless steel.

Misalnya:

• Nitric acid: Stainless steel resists attack, while carbon steel shows rust or bubbling

• Copper sulfate: Reacts with carbon steel (copper plating visible) but not with stainless steel

These are semi-quantitative methods and give a reliable field indication of the material composition.

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6. Material Markings and Stamping

Reputable manufacturers like sasa lonjong mark each flange with:

• Kelas materi (misalnya, SS316, A105)

• Peringkat tekanan (misalnya, 150#, 300#)

• Ukuran dan jadwal

• Standar (misalnya, ASME B16.5)

• Nomor panas for traceability

Always check the stamping on the flange rim or hub. If a flange lacks clear markings, it should be tested before installation.

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7. Identifikasi Material Positif (PMI)

The most accurate way to distinguish flange material is pengujian PMI using handheld analyzers like XRF (X-ray fluorescence) atau LIBS (laser-induced breakdown spectroscopy).

These devices provide:

• Elemental composition (misalnya, Kr, Di dalam, Fe, Mo)

• Grade matching (misalnya, confirms 316L vs 304)

• Instant results in the field or warehouse

PMI is often required for critical systems in minyak & gas, bejana tekan, and food processing equipment.

sasa lonjong offers full PMI testing and certification for stainless steel and carbon steel flange deliveries upon request.

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8. Corrosion Behavior

Expose a small, cleaned section of the flange to salt water spray or a humid environment for 24–48 hours.

• Baja karbon: Will show visible rust or reddish discoloration

• Baja tahan karat: Remains clean or may develop a light surface film, but no red rust

This simple exposure test helps confirm the corrosion resistance typical of stainless steel.

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Applications Based on Flange Material