Fusion-bonded epoxy-coated reinforcing bars

IS 13620: Scope and Key Specifications

• Scope:
  Covers deformed steel reinforcing bars with fusion bonded epoxy coating applied by electrostatic spray for corrosion protection in concrete structures.

• Purpose:
  Protect reinforcement bars from corrosion, especially in saline or industrially polluted environments, complementing good construction practices.

• Coating Adhesion Test (Clause 8.3):

  • Bars are bent 120° around a mandrel (size per Table 1) at 25–35°C.
  • Bend test duration: up to 90 seconds.
  • Partial steel fracture is not considered coating failure.

• Mandrel Diameter Table for Bend Test:

• Reference Standards:
  • IS 1786 for steel bars
  • ASTM A775/A775M and D3963 for epoxy-coated bars

This standard ensures quality epoxy-coated bars for enhanced durability in corrosive environments.

IS 13620: Key References, Formulas, and Tables Summary

1. Adhesion of Coating (Clause 8.3)

• Test: Bend coated bars 120° around a mandrel (after rebound).
• Test Conditions: Uniform bending rate, max 90 seconds, temperature 25–35°C.
• Note: Partial steel fracture ≠ coating adhesion failure.

2. Mandrel Diameter for Bend Test (Table 1)

3. Hardness Test (Clause 8.1)

• Knoop hardness tester, 10 g load.
• Minimum average Knoop Hardness Number: 16.

4. References & Related Standards

• IS 1786: High strength deformed steel bars.
• IS 6885: Knoop hardness testing.
• ASTM A775/A775M-84, ASTM D3963-1986: Epoxy-coated bars specs.

Summary Diagram: Bend Test Setup

graph LR
A[Coated Bar] --> B(Bend 120° around Mandrel)
B --> C[Mandrel Diameter per Table 1]
C --> D[Test at 25-35°C]
D --> E[Check Coating Adhesion]

This ensures quality epoxy-coated bars for corrosion resistance in RCC structures per IS 13620.

IS 13620: Key Specifications for Coating Materials (Organic Coatings)

1. Coating Material Requirements (Clause 3.1, Annex A):

• Coating materials must comply with Annex A requirements.
• Pigments, if used, should be inorganic compounds.
• Chemical resistance per Clause A-2 must be ensured.

2. Coating Thickness (Clause 7.1 & 7.1.1):

• Thickness range: 0.1 mm to 0.3 mm after curing.
• Acceptance criteria: At least 90% of measurements must lie within this range.
• Measurement: Minimum 15 readings evenly spaced along each side of the test bar.
• Patched areas: Thickness limits do not apply.
• Note: Thicker coatings may be accepted if bars are not bent or worked post-coating.

Summary Table for Coating Thickness Acceptance

flowchart LR
    A[Coating Material] --> B[Meets Annex A Requirements]
    B --> C[Chemical Resistance Check]
    C --> D[Apply Coating on Bars]
    D --> E[Measure Thickness (≥15 per side)]
    E --> F{≥90% within 0.1-0.3 mm?}
    F -- Yes --> G[Accept Coating]
    F -- No --> H[Reject or Recoat]

This ensures durability and performance of coated reinforcement bars as per IS 13620.

IS 13620: Surface Preparation for Coated Steel Reinforcing Bars

Key Specifications (Clauses 5.1 & 5.2)

• Surface Cleaning:

  • Abrasive blast cleaning to near white metal finish.
  • Surface must be free from mill scale, rust, and foreign matter under well-lit conditions.

• Timing for Coating Application:

  • Coating must be applied as soon as possible after cleaning.
  • If rust blooms appear, re-blast cleaning is required before coating.
  • Coating delay must not exceed 8 hours unless purchaser permits.

Additional Notes on Application (Clause 6)

• Coating applied by electrostatic dry powder spray onto grounded bars.
• Bars can be coated hot or cold.
• Thermal curing per epoxy resin manufacturer’s recommendations to avoid defects.

Summary Table: Surface Preparation & Coating Timing

This ensures optimal adhesion and durability of the epoxy coating on reinforcing bars, critical for corrosion protection.

flowchart TD
    A[Steel Bar Surface] --> B[Abrasive Blast Cleaning]
    B --> C{Surface Clean?}
    C -- Yes --> D[Apply Coating (Electrostatic Spray)]
    C -- No --> B
    D --> E[Thermal Curing as per Manufacturer]
    E --> F[Finished Coated Bar]

IS 13620 - Application of Coating: Key Points

1. Coating Thickness (Clause 7.1 & 7.1.1)

• Thickness range: 0.1 mm to 0.3 mm after curing.
• Sampling: Minimum 15 measurements evenly spaced along each side of the bar.
• Acceptance: At least 90% of measurements must fall within the specified range.
• Note: Thicker coatings allowed if bars are not bent/worked post-coating (by mutual agreement).

2. Coating Material (Clause 3.1 & A-1)

• Organic coatings with pigments (if used) must be inorganic compounds.
• Must comply with chemical resistance requirements (A-2 to A-8).

3. Application Procedure (Clause 5.2 & 6)

• Apply coating immediately after cleaning (within 8 hours).
• Remove rust blooms by blast cleaning before coating.
• Use electrostatically charged dry powder spray on grounded steel bars.
• Bars can be coated hot or cold.
• Thermal curing as per epoxy resin manufacturer’s instructions to avoid defects.

Summary Table: Coating Thickness Acceptance

flowchart LR
    A[Surface Cleaning] --> B{Rust Bloom?}
    B -- Yes --> C[Blast Cleaning]
    B -- No --> D[Apply Coating]
    C --> D
    D --> E[Electrostatic Powder Spray]
    E --> F[Thermal Curing per Manufacturer]
    F --> G[Coating Thickness Check]
    G --> H{≥ 90% between 0.1-0.3 mm?}
    H -- Yes --> I[Accept Coated Bars]
    H -- No --> J[Rework or Reject]

This ensures durable, defect-free coated reinforcement bars as per IS 13620.

IS 13620: Key Specifications & Formulas for Requirements of Coated Bars

1. Coating Application (Clause 6)

• Coating: Electrostatic dry powder sprayed on cleaned bars.
• Thermal curing per epoxy manufacturer’s recommendations.
• Temperature control is critical to avoid defects like blistering.

2. Adhesion Test (Clause 8.3)

• Bend coated bars 120° around a mandrel at uniform speed (up to 90 sec).
• Test at 25°C to 35°C thermal equilibrium.
• Partial steel fracture ≠ coating adhesion failure.

3. Mandrel Diameter for Bend Test (Table 1)

4. Gauge Correction Factor (Clause 8.1.3)

[ \text{Correction Factor} = \overline{G}{cleaned\ uncoated} - \overline{G}{mild\ steel\ plate} ]

• Average 10 gauge readings on cleaned uncoated bar minus average 5 readings on mild steel plate.
• Subtract this factor from all coated bar gauge readings.

5. Frequency & Quality Control (Clause 13.4)

• Patching per manufacturer’s instructions.
• Non-conforming samples are rejected or reprocessed after stripping and recoating.

Summary Flow of Coated Bar Quality Control:

flowchart TD
    A[Cleaning of Bars] --> B{Within 8 hours?}
    B -- Yes --> C[Apply Electrostatic Powder Coating]
    B -- No --> D[Re-clean and Recoat]
    C --> E[Thermal Curing as per Manufacturer]
    E --> F[Bend Test (120° around Mand

IS 13620 - Coating Thickness Key Points

1. Coating Thickness Limits (Clause 7.1.1)

• Acceptance criteria:
  • At least 90% of measurements must be between 0.1 mm and 0.3 mm after curing.
  • Minimum 15 measurements per side of the test bar, evenly spaced.
  • Limits do not apply to patched areas.
• Note: Thicker coatings may be accepted if bars are not bent/worked post-coating (by mutual agreement).

2. Measurement Method (Clause 8.1)

• Measure coating thickness on the body of the bar, between ribs/deformations, on a straight length.
• Use non-destructive magnetic gauges.

3. Correction Factor for Gauge Readings (Clause 8.1.3)

• Calculate correction factor (CF) as:
  [ CF = \text{Average of 10 gauge readings on cleaned, uncoated bar} - \text{Average of 5 gauge readings on smooth mild steel plate} ]
• Apply correction:
  [ \text{Corrected coating thickness} = \text{Gauge reading on coated bar} - CF ]

Summary Table

flowchart LR
  A[Cleaned Uncoated Bar] -->|10 readings avg| B[Average Bar Reading]
  C[Smooth Mild Steel Plate] -->|5 readings avg| D[Average Plate Reading]
  B --> E[Calculate CF = B - D]
  F[Coated Bar Reading] --> G[Subtract CF]
  G --> H[Corrected Coating Thickness]

This ensures accurate, consistent coating thickness evaluation per IS 13620.

IS 13620 - Adhesion of Coating (Clause 8.3)

Key Test Method:

• Bend Test: Production coated bars are bent 120° (after rebound) around a mandrel.
• Test Conditions:
  • Uniform bending rate, completed within 90 seconds.
  • Bars at thermal equilibrium: 25℃ to 35℃.
  • Longitudinal deformations perpendicular to mandrel radius.
• Note: Partial steel bar fracture during bending is not considered coating adhesion failure.

Mandrel Diameter for Bend Test (Table 1):

Summary:

• The bend test evaluates coating adhesion by bending bars around a mandrel sized per bar diameter.
• No coating detachment should occur after bending.
• Test must be done at controlled temperature and speed.

flowchart LR
    A[Coated Bar] --> B[Bend 120° around Mandrel]
    B --> C{Mandrel Diameter}
    C -->|Based on Bar Dia| D[Table 1]
    B --> E[Check for Coating Detachment]
    E -->|No Detachment| F[Pass Adhesion Test]
    E -->|Detachment| G[Fail Adhesion Test]

IS 13620: Resistance to Chemical and Mechanical Damage for Organic Coatings

Chemical Resistance (Clause A-2)

Coated bars must be immersed in these solutions to evaluate chemical resistance:

• Distilled water
• 3 M CaCl₂ aqueous solution
• 3 M NaOH aqueous solution
• Saturated Ca(OH)₂ solution

Acceptance: No visible deterioration or loss of adhesion after immersion.

Mechanical Resistance

Summary Table

flowchart LR
    A[Coating Material] --> B[Chemical Resistance Test]
    B --> C{Solutions}
    C --> D[Distilled Water]
    C --> E[3 M CaCl2]
    C --> F[3 M NaOH]
    C --> G[Saturated Ca(OH)2]
    A --> H[Mechanical Resistance Test]
    H --> I[Abrasion: Taber Abrasor]
    H --> J[Impact: Falling Weight Test]

This ensures durability of coatings against chemical attack and mechanical damage per IS 13620.

IS 13620: Bond Strength to Concrete - Key Points

• Test Method: Pull-out test as per IS 1786:1985 (modified in A-5.2 to A-5.8).
• Specimens: Two coated and two uncoated bars, 20 mm diameter.
• Measurement: Bond strength calculated at slips of 0.025 mm and 0.25 mm.
• Coating Integrity: No visible cracking on bent bars (Clause A-4.2).
• Bond Strength Requirement:
  [ f_{b, coated} \geq 0.8 \times f_{b, uncoated} ] where (f_b) = mean bond strength at specified slip.
• Failure Criterion: Bond failure when slip > 0.2 mm at free end under axial load (Clause A-5.3).

Summary Table for Bond Strength Test

This ensures coated bars maintain adequate bond performance compared to uncoated bars, critical for structural integrity.

IS 13620: Handling and Identification of Coated Bars

Key Specifications from IS 13620:

• Handling (Clause 11.1):

  • Use padded contact areas on all handling systems.
  • Bundling bands must be padded or suitable to prevent coating damage.
  • Lift bundles with strong backs, spreader bars, multiple supports, or platform bridges to avoid bar-to-bar abrasion.
  • Bars/bundles must not be dropped or dragged.

• Identification (Clause 16.2.1):

  • Each bundle must have a tag showing:
    • Cast No./Lot No.
    • Grade
    • Size of bars.

• Coating Failure Retesting (Clause 10.1):

  • If initial coating thickness/adhesion test fails, test twice the original number of samples.
  • If retests pass, accept the batch; otherwise, reject or reprocess.

• Patching (Clause 13.4):

  • Follow patching material manufacturer’s instructions strictly.

• Manufacturer’s Certificate (Clause 15):

  • On request, provide a certificate confirming compliance with IS 13620 requirements.

Summary Table: Handling & Identification

flowchart LR
    A[Coated Bars] --> B[Handling]
    B --> C{Padded Contact?}
    C -->|Yes| D[Safe Handling]
    C -->|No| E[Risk of Coating Damage]
    B --> F{Bundling Bands Padded?}
    F -->|Yes| D
    F -->|No| E
    A --> G[Identification]
    G --> H[Tag with Cast No., Grade, Size]
    A --> I[Testing]
    I --> J{Initial Test Pass?}
    J -->|Yes| K[Accept Batch]
    J -->|No| L[Test

IS 13620 - Permissible Coating Damage and Repair

Key Specifications from IS 13620:

• Permissible Damage Size:

  • Coating damage ≤ 40 mm² due to fabrication or handling need not be repaired (Clause 13.1).

• Repair Material Requirements:

  • Must be compatible with the original coating.
  • Should be inert in concrete (non-reactive).
  • Feasible for repair at the coating plant or field.
  • Must be approved by the purchaser before use (Clause 3.2).
  • Repair must follow manufacturer's recommendations.

Summary Table:

Additional Notes:

• Identification of rebars must be maintained throughout fabrication and coating (Clause 11.2).
• All tests and inspections should be done before shipment unless specified otherwise.

flowchart TD
    A[Fabrication & Handling] --> B{Damage Area ≤ 40 mm²?}
    B -- Yes --> C[No Repair Needed]
    B -- No --> D[Repair Required]
    D --> E[Use Compatible & Approved Material]
    E --> F[Repair as per Manufacturer's Instructions]
    F --> G[Shipment]

This ensures coating integrity and corrosion protection per IS 13620.

Manufacturer's Certificate (IS 13620 Clause 15)

• Upon purchaser's request, the manufacturer must provide a written certificate at shipment confirming that the coated reinforcing bars comply with IS 13620 requirements.
• The certificate should reference:
  • Compliance with coating thickness (0.1 mm to 0.3 mm for 90% of measurements, Clause 7.1.1).
  • Results of adhesion tests (bend test per Clause 8.3 and Table 1).
  • Confirmation of patching done as per manufacturer's recommendations (Clause 13.4).
  • Any standard mark if applied (Clause 16.2).

Key Specifications Summary

Table 1: Mandrel Diameter for Bend Test (Clause 8.3)

flowchart TD
    A[Manufacturer] -->|Shipment| B[Purchaser]
    B -->|Requests| C[Manufacturer's Certificate]
    C --> D[Confirms Coating Thickness]
    C --> E[Confirms Adhesion Bend Test]
    C --> F[Confirms Patching Compliance]
    C --> G[Includes Standard Mark if applicable]

Note: Bars failing coating tests may be stripped, recoated, and retested by mutual agreement.

IS 13620: Marking and Traceability of Coated Reinforcing Bars

Key Specifications:

• Clause 16.1:
  Bars must be marked to trace every finished bar back to its cast or original identification mark.

• Clause 16.2.1:
  Each bundle must have a tag showing:

  • Cast No./Lot No.
  • Grade
  • Size of bars

• Manufacturer’s Certificate (Clause 15):
  On request, a certificate confirming compliance with the specification must be provided at shipment.

Testing & Acceptance (related to traceability):

• If coating tests fail, double the original sample size must be retested (Clause 10.1).
• If retests pass, the batch is accepted, ensuring traceability of quality.

Summary Table for Marking & Traceability

flowchart LR
    A[Finished Bars] --> B[Mark with Cast/Lot No.]
    B --> C[Bundle Bars]
    C --> D[Attach Tag: Cast/Lot No., Grade, Size]
    D --> E[Shipment]
    E --> F{Certificate Requested?}
    F -- Yes --> G[Provide Manufacturer's Certificate]
    F -- No --> H[Complete Process]

This ensures full traceability from cast to site delivery, critical for quality control and accountability.

IS 13620 - Testing Methods & Quality Control Summary

1. Adhesion of Coating (Clause 8.3)

• Test: Bend coated bars 120° around a mandrel at uniform rate (up to 90 sec).
• Temperature: Test at thermal equilibrium (25℃–35℃).
• Mandrel Diameter: As per bar diameter from Table 1:

• Note: Partial steel fracture during bend test ≠ coating adhesion failure.

2. Hardness Test (Clause 8.1)

• Method: Knoop hardness tester (IS 6885:1973), 10 g load.
• Requirement: Average Knoop Hardness Number ≥ 16 (4 measurements between ribs on 2 bars).

3. Frequency of Testing (Clause 10.1)

• If a sample fails coating thickness or adhesion test, double the sample size for retesting.
• If retests pass, accept the batch.

4. Abrasion Resistance (Clause A-6.1)

• Test: Taber abrasor with CS-10 wheels, 1 kg load.
• Limit: Weight loss ≤ 100 mg per 1000 cycles.

flowchart TD
    A[Start Testing] --> B{Coating Adhesion Test}
    B -->|Pass| C[Accept Batch]
    B -->|Fail| D[Double Sample Size Retest]
    D --> E{Retest Pass?}
    E -->|Yes| C
    E -->|No| F[Reject Batch]

Summary: IS 13620 mandates bend tests with specific mandrel sizes, Knoop hardness ≥16, controlled abrasion loss, and retesting protocols to ensure