Característica	Brida de acero inoxidable	Carbon Steel Flange
Main Alloy Elements	Hierro, Cromo (≥10.5%), Níquel	Hierro, Carbón (0.2–0.6%)
Resistencia a la corrosión	Excelente	Bajo (requires coating or lining)
Appearance	Silvery, bright, non-rusting	Dull gray, prone to rust
Magnetic Property	Usually non-magnetic (austenitic)	Magnetic
Costo	Más alto	Más bajo
Typical Grades	SS304, SS316, SS321	ASTM A105, A350 LF2, Q235

1. Inspección visual

Stainless steel flanges generally have a bright silver finish and resist oxidation. Even after extended exposure to air and moisture, they maintain a clean, shiny surface.

Bridas de acero al carbono, por otro lado, often appear dull gray or matte black. Without protective coatings like paint, galvanizado, o aceite, carbon steel flanges will óxido con el tiempo.

Visual differences:

• Acero inoxidable: Polished or satin finish, clean look, no surface corrosion

• Acero carbono: Dull, may have red/brown rust spots or black oxide coating

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

---

2. Magnet Test

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

• Acero carbono is always magnético

• Acero inoxidable varies:

  • Austenitic grades (p.ej., SS304, SS316): No magnético or slightly magnetic

  • Ferritic and martensitic grades: Magnetic

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 acero inoxidable austenítico.

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

---

3. Spark Test

The spark test is commonly used in metal workshops:

• Acero carbono produces largo, branching orange sparks when touched with a grinder

• Acero inoxidable 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.

---

4. Weight Comparison

Stainless steel is 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.

---

5. Chemical Testing with Spot Kits

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

Por ejemplo:

• 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.

---

6. Material Markings and Stamping

Fabricantes de renombre como Sasaflange mark each flange with:

• Grado de material (p.ej., SS316, A105)

• Clasificación de presión (p.ej., 150#, 300#)

• Tamaño y horario

• Estándar (p.ej., ASME B16.5)

• número de calor for traceability

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

---

7. Identificación positiva de materiales (PMI)

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

These devices provide:

• Elemental composition (p.ej., cr, En, fe, Mes)

• Grade matching (p.ej., confirms 316L vs 304)

• Instant results in the field or warehouse

PMI is often required for critical systems in aceite & gas, recipientes a presión, and food processing equipment.

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

---

8. Corrosion Behavior

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

• Acero carbono: Will show visible rust or reddish discoloration

• Acero inoxidable: 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.

---

Applications Based on Flange Material