Water Cleaning

Why Washing is Required Before Abrasive Blasting

Preparation of the surface is the most critical operation before painting. It has often been seen that coating failures are not due to the qual

ity of the paint, but the quality of the preparation. The first operation before abrasive blasting is the washing of the surface.

In the following article, you are going to get detailed information about the need for washing before abrasive blasting.

1️⃣ What is Washing Before Abrasive Blasting?

Washing means the removal of:

Oil

Grease

Salt Contamination

Dust

Mud

Chemical Residue

This process is carried out before blasting the surface.

As per the international surface preparation standards like

👉 ISO 8501-1

contamination has to be removed before proper blasting can be carried out.

2️⃣ Why is Washing Important Before Blasting?

🔹 1. Removes Oil and Grease

Abrasive blasting cannot remove oil and grease properly.

If oil is present:

Oil spreads over the surface during blasting

Oil contaminates the abrasive

Oil reduces the adhesion of the coating

Washing removes these contaminants properly.

🔹 2. Avoids Salt Contamination

In the areas around the sea, steel surfaces are generally contaminated with salt.

If salts are present:

Coating blisters

Corrosion occurs under the paint

Paint peels quickly

Water washing removes soluble salts properly.

🔹 3. Improves Blasting Efficiency

If the dirt and mud are removed:

The abrasive material hits clean metal

Blasting is faster

Less abrasive is consumed

Improved surface profiles are obtained

This saves the project costs.

🔹 4. Prevents Abrasive Contamination

If the washing is not done:

Oil is mixed with the abrasive

The abrasive becomes dirty

Quality of the abrasive is reduced

Clean surface means clean abrasive.

🔹 5. Ensures Proper Inspection

If the washing is done:

The surface defects are seen

Cracks and weld defects can be inspected

Inspector can determine the proper blasting level (Sa 2, Sa 2.5, Sa 3)

3️⃣ Types of Washing Before Blasting

✅ 1. Fresh Water Washing

This is done to remove:

Dust

Mud

Loose contaminants

This is common in general industrial projects.

✅ 2. High-Pressure Water Washing

This is done to remove:

Salts

Thick dirt

Marine contaminants

This is common in offshore and refinery projects.

✅ 3. Detergent Cleaning

This is done to remove:

Heavy oils

Grease

Chemical contaminants

Fresh water is required after detergent cleaning.

4️⃣ What Happens If Washing Is Not Done?

If washing is not carried out, the following may occur:

❌ Poor coating adhesion

❌ Early rusting

❌ Blistering

❌ Paint peeling

❌ Rejection of the project by the inspector

These are the main reasons for coating failure, as salt may contaminate the surface before blasting.

5️⃣ Standard Practice in Industry

According to ISO standards, the following practices are required:

Degreasing of the surface

Washing of the surface with clean water

Drying of the surface

Finally, abrasive blasting to a required standard (Sa 2.5 or Sa 3)

Proper washing of the surface is essential to attain the required level of cleanliness according to:

👉 ISO 8501-1

6️⃣ Drying After Washing

Before starting the blasting of the surface, the following must be ensured:

The surface must be completely dry

There must be no standing water on the surface

There must be no moisture on the surface

Moisture may lead to flash rusting on the surface.

8️⃣ Safety During Washing

Proper use of PPE

Control of water runoff

Environmental regulations

Prevention of water entering electrical systems

Conclusion

Washing prior to abrasive blasting is not an option, but a necessity.

It is essential in the removal of oil, grease, salts, and contaminants that cannot be removed by blasting alone.

Proper washing is essential to ensure improved surface preparation, adhesion, and life of the coating.

In painting, skipping the washing process can result in failure of the coating, thus incurring additional repair costs.