Abrasive Blasting Process

The abrasive blasting process is a way to get a surface ready for coating or painting. It is used to clean and roughen up metal, concrete and other surfaces. This process is very important because it helps the coating stick to the surface and last longer.
Main Purpose of Abrasive Blasting
The main purpose of blasting is to
Remove rust, mill scale, old paint and contaminants
Create a surface profile, which is like a pattern that helps the coating stick
Improve how well the coating sticks to the surface
Get the surface ready according to certain standards like
SSPC
NACE International
Saudi Aramco coating specifications

Abrasive Blasting Process Steps

1. Surface Inspection

Before you start blasting you need to
Check how much rust is on the surface
Look for oil, grease, salts or old coatings
Check the temperature, humidity and dew point
2. Surface Cleaning
You need to remove oil and grease first using a solvent. This is according to the SSPC-SP1 standard.
If you do not remove contaminants the blasting will not be as good.

Abrasive Blasting Process

3. Abrasive Selection

There are types of abrasives. Some common ones are
Garnet, which is used for industrial blasting
Steel Grit, which is used for heavy-duty cleaning
Steel Shot, which is used for peening the surface
Aluminum Oxide, which is used for aggressive blasting
Copper Slag, which is used to remove rust quickly
Glass Beads, which are used for light finishing work

4. Equipment Setup

The main equipment you need for blasting is
An air compressor
A blast pot
A blast hose
A nozzle
A moisture separator
protective equipment
The nozzle pressure is usually between 90 and 110 PSI.

5. Blasting Operation

The person doing the blasting
Holds the nozzle at an angle of 45 to 90 degrees
Keeps the distance from the surface
Moves the nozzle evenly across the surface
The abrasive hits the surface hard to remove contaminants and create a profile.

Common Blasting Standards

There are many standards for blasting. Some of them are
SSPC-SP5, which's a white metal blast
SSPC-SP10, which is a near white blast
SSPC-SP6, which is a commercial blast
SSPC-SP7, which is a brush-off blast

Surface Profile

The surface profile is how rough the surface is after blasting.
The typical profile range is 40 to 75 microns for coatings.
You can measure the profile using
Replica tape
A surface profile gauge

Safety Requirements

You need to wear safety gear when blasting, such as
A blast helmet with an airline
A respirator
Gloves
Safety boots
Hearing protection
There are many hazards when blasting, including
Breathing in dust
Abrasive particles flying around
Static electricity
Noise

Common Problems During Blasting

There are many problems that can happen when blasting. Some of them are
Flash rust, which happens when it is humid
Low profile, which happens when you use the wrong abrasive
Dust contamination, which happens when the compressed air is wet
Uneven surface, which happens when you move the nozzle wrong

Applications

Abrasive blasting is used in many places, such, as
Oil and gas plants
Pipelines
Storage tanks
Offshore structures
Shipyards
Structural steel fabrication

Key Inspection Checks

After blasting you need to check
How clean the surface is
The surface profile
For dust
For chloride contamination
Do a visual inspection
You should start painting quickly after blasting to avoid flash rusting.