Salt contamination
is a problem that causes coatings to fail and corrode in industrial painting. Even if a surface looks clean there can still be salts that cause blisters, rust and poor adhesion.
A salt contamination test is done to find out how many soluble salts are on a surface before any coating is applied.
A salt contamination test is done to find out how many soluble salts are on a surface before any coating is applied.
What is Salt Contamination?
Salt contamination happens when there are salts like chlorides, sulfates and nitrates on a surface.These salts attract moisture from the air. Cause corrosion under the coating.
⭐Chlorides (Cl⁻)
⭐Sulfates (SO₄²⁻)
⭐Nitrates (NO₃⁻)
It prevents coatings from failing soon.
It helps the paint stick to the surface better.
It reduces the risk of corrosion.
It makes sure that the project is done according to the specifications.
It also helps the coating longer.
It can come from environments like sea water and coastal areas.
It can also come from pollution.
Contaminated abrasive blasting materials can cause it.
If someone handles a surface with sweaty hands it can get contaminated.
Previous exposure to services can also cause salt contamination.
Here is how it works:
You attach a Bresle patch to the surface.
Then you inject distilled water into the patch.
The salts on the surface dissolve in the water.
You extract the solution. Measure how conductive it is.
The result is shown in micrograms per centimeter.
If the conductivity is high it means that there is a lot of salt contamination.
They give results that you can get on site.
Generally if the salt level is less than or equal to 5 micrograms per square centimeter it is excellent.
If it is between 5 and 10 micrograms per centimeter it is acceptable.
If it is than 10 micrograms per square centimeter the surface needs to be cleaned.
Why Salt Contamination Testing is Important
Salt contamination testing is important for reasons.It prevents coatings from failing soon.
It helps the paint stick to the surface better.
It reduces the risk of corrosion.
It makes sure that the project is done according to the specifications.
It also helps the coating longer.
Common Sources of Salt Contamination
There are ways that salt contamination can happen.It can come from environments like sea water and coastal areas.
It can also come from pollution.
Contaminated abrasive blasting materials can cause it.
If someone handles a surface with sweaty hands it can get contaminated.
Previous exposure to services can also cause salt contamination.
Methods of Salt Contamination Testing
There are a ways to test for salt contamination.1. Bresle Test
The Bresle test is the widely used method.Here is how it works:
You attach a Bresle patch to the surface.
Then you inject distilled water into the patch.
The salts on the surface dissolve in the water.
You extract the solution. Measure how conductive it is.
The result is shown in micrograms per centimeter.
2. Conductivity Meter Method
This method measures how conductive the extracted solution is.If the conductivity is high it means that there is a lot of salt contamination.
3. Chloride Test Kits
These kits are used to detect chloride contamination.They give results that you can get on site.
Acceptable Salt Levels
The acceptable salt levels can vary depending on the project.Generally if the salt level is less than or equal to 5 micrograms per square centimeter it is excellent.
If it is between 5 and 10 micrograms per centimeter it is acceptable.
If it is than 10 micrograms per square centimeter the surface needs to be cleaned.
⭐≤ 5 µg/cm² → Excellent
⭐5–10 µg/cm² → Acceptable
⭐> 10 µg/cm² → Requires cleaning
ISO 8502-6 is for extracting salts.
ISO 8502-9 is a field method for measuring salt.
SSPC Guide 15 is for field methods for salts.
NACE SP0508 is for methods for surface cleanliness.
It can cause blisters to form on the coating.
It can create pressure.
It can cause rust to form under the coating.
It can reduce the adhesion of the coating.
It can cause the coating to break down early.
You can wash the surface with water.
You can use high-pressure water jetting.
You can use steam cleaning.
You need to prepare the surface
You need to use distilled water.
You need to calibrate the conductivity meter.
You need to avoid contaminating the surface during testing.
You need to do the test before painting.
You need to take readings.
Salt contamination testing is very important to make sure that the surface is clean and the coating will last.
By detecting and removing salts before painting you can significantly improve the performance of the coating. Prevent costly failures.
---
Standards for Salt Testing
There are a few standards that are used for salt testing.ISO 8502-6 is for extracting salts.
ISO 8502-9 is a field method for measuring salt.
SSPC Guide 15 is for field methods for salts.
NACE SP0508 is for methods for surface cleanliness.
Effects of High Salt Contamination
salt contamination can cause a lot of problems.It can cause blisters to form on the coating.
It can create pressure.
It can cause rust to form under the coating.
It can reduce the adhesion of the coating.
It can cause the coating to break down early.
How to Remove Salt Contamination
There are a ways to remove salt contamination.You can wash the surface with water.
You can use high-pressure water jetting.
You can use steam cleaning.
You need to prepare the surface
Tips, for Accurate Testing
There are a things you need to do to get accurate test results.You need to use distilled water.
You need to calibrate the conductivity meter.
You need to avoid contaminating the surface during testing.
You need to do the test before painting.
You need to take readings.
Salt contamination testing is very important to make sure that the surface is clean and the coating will last.
By detecting and removing salts before painting you can significantly improve the performance of the coating. Prevent costly failures.
---
Tags:
Technical testing