Internal pipe coating is one of the most effective ways to protect pipelines from rust, corrosion, chemicals, and wear. Whether a pipe carries water, oil, gas, or chemicals, coating the inside keeps it strong and clean for many years.

This guide explains everything in simple English, step-by-step, so even someone new to the industry can understand the full process.

What Is Internal Pipe Coating?

Internal pipe coating is the process of applying a protective layer inside a pipe. This layer acts like a tough inner skin that shields the pipe from:

rust
dirt
moisture
chemical attack
friction and wear

Because of the coating, the pipe lasts longer and the flow inside stays smooth and clean.

Why Is Internal Pipe Coating Important?

Benefits:

Prevents rust and corrosion
Reduces maintenance costs
Increases pipeline lifespan
Improves flow efficiency
Stops contamination (important for drinking water pipelines)
Works for oil, gas, water, fire-fighting lines, and industrial pipes

1. Surface Preparation for Internal Pipe Coating

Preparing the pipe surface is the most important step.
If the surface is not clean, the coating will not stick well.

Step-by-Step Preparation

Initial Cleaning
Remove grease, oil, and mud using detergents or high-pressure water.

Drying
The pipe must be completely dry.
Moisture will cause the coating to bubble or peel.

Surface Roughening
The inside of the pipe must be made slightly rough so the coating bonds strongly.

2. Blasting Standard (Sa 2.5) for Internal Pipes

Abrasive blasting is used to clean the pipe to international standards.

What Is Sa 2.5?

Sa 2.5 is a blasting cleanliness standard that means:

Almost all rust removed
Very small stains allowed
Surface is bright and rough
Roughness between 50–100 microns

Media Used for Blasting

Steel grit
Steel shot
Garnet

Special blasting heads are sent inside the pipe to clean evenly.

3. Inspection Tests Before Coating

Before applying coating, the pipe must be inspected.

Inspection Checklist
Visual inspection: Using lights or cameras
Roughness test: Must be between 50–100 microns
Cleanliness test: No oil, dust, or moisture
Wipe test: Clean white cloth should show no dirt

If any test fails, blasting must be repeated.

4. Internal Pipe Coating Machines

An internal pipe coating machine sprays coating material inside the pipe.

How It Works (Simple)
A spray head enters the pipe
The head rotates at high speed
It moves forward at a controlled speed

The coating spreads evenly inside the pipe

Pipe Sizes Supported

Most machines work for 3–35 inch pipes.

5. Internal Pipe Coating Equipment

To complete the job smoothly, several tools are needed:

Essential Equipment
Abrasive blasting tools
RotorSpray or ConeSpray units
High-pressure airless spray pumps
Mixing tanks
Heating units (if needed)
Pipe end protectors
Thickness gauges and inspection tools
Good equipment ensures an even, strong, long-lasting coating.

6. Internal Pipe Coating Process (Step-By-Step)

1. Blasting

Clean and roughen the pipe interior.

2. Surface Inspection

Check roughness, cleanliness, and dryness.

3. Mixing the Coating Material

Mix epoxy, FBE, or polyurethane according to manufacturer instructions.

4. Coating Application

Spray the coating while the pipe rotates or while the spray head moves through it.

5. Curing

Drying may take:

natural air curing

heated curing (for FBE or thick coatings)

6. Final Inspection

Check thickness, smoothness, and uniformity.

7. Coating Types (Internal Pipe Coating Solutions)1. Epoxy Coating (Most Popular)

Strong adhesion
Good for water, oil, and gas
Resists chemicals

2. Fusion Bonded Epoxy (FBE)

High-temperature resistance
Very strong bonding
Used in oil & gas pipes

3. Polyurethane Coating

Best chemical resistance
Flexible and durable

8. Internal Pipe Coating Sprayer

The sprayer is the key to achieving even coverage.

Tip Size

0.015 to 0.025 inches
Larger tips for thick coatings

Why Airless Sprayers?

Smooth finish
No air bubbles
Consistent pressure
Better penetration

9. Complete Internal Pipe Coating Systems

A full system usually includes:

Blasting unit
Coating machine
Curing system
Inspection tools

Brands like Airblast, Andersen, and Wagner supply complete coating systems that work for straight and bent pipes.

10. Coating Thickness

Typical thickness depends on pipe service:

Minimum: 200–300 microns
Heavy-duty: 500–1000 microns
Layers: Usually 3–6 coats
Drying time: Around 48 hours

Conclusion

Internal pipe coating is a reliable and cost-effective way to extend the life of pipelines used in water, oil, gas, and industrial systems. With proper cleaning, correct blasting, careful inspection, and the right coating material, pipelines can stay protected for many years.

FAQs

1. What does internal pipe coating do?

It protects the inside of pipes from rust, corrosion, and chemical damage.

2. Why is blasting important?

It removes rust and creates a rough surface that helps the coating stick.

3. Which coating is best?

Epoxy is the most commonly used coating for water, oil, and gas pipes.

4. How thick should the coating be?

Between 200 and 1000 microns depending on pipe conditions.

5. How do I know if the surface is ready for coating?

Check roughness, cleanliness, and dryness with inspection tools.

6. Can bent pipes be coated?

Yes. Flexible spray heads can coat straight and curved pipes.

7. How long does curing take?

Around 48 hours for full hardness.

Credit: Video and images sourced from the YouTube video referenced above. All rights belong to the original creator.

Internal Pipe Coating | A Simple and Complete Guide for Beginners