Immersion Service Coating Systems

Immersion service coating systems are coatings that help protect surfaces that are always or often under water or other liquids like seawater, chemicals, crude oil, wastewater or process fluids. These systems help prevent corrosion, resist chemicals and last a long time in harsh environments.

What Is an Immersion Service Coating

An immersion coating system helps protect steel or concrete structures that are exposed to things like
   water all the time
   saltwater
   chemicals
   wastewater treatment
   oil and gas processing
   ballast tanks and pipelines
Immersion coatings are different from coatings because they have to resist
   water getting in
   blisters from water
   chemicals attacking them
   damage from cathodic protection
   wear and tear from moving liquids

Immersion Service Coating Systems

Common Areas Using Immersion Coatings

Immersion coatings are used in many places like
   Marine Industry: ship ballast tanks, offshore platforms, seawater pipelines, jetties and docks
   Oil & Gas: crude oil tanks, produced water tanks, underground pipelines, separator vessels
    Water Treatment Plants: clarifiers, water storage tanks, wastewater basins
     Industrial Plants: chemical tanks, process vessels, cooling water systems

Types of Immersion Service Coatings

1. Epoxy Coatings

Epoxy coatings are the common type of immersion coating. They are very good at sticking to surfaces, resisting water and resisting chemicals. They are also strong.
Typical uses for epoxy coatings include
   water tanks
   ballast tanks
  wastewater systems

2. Novolac Epoxy Coatings

Novolac epoxy coatings are used when the chemicals are very harsh. They are very good at resisting chemicals can handle temperatures and resist solvents.
Typical uses for novolac epoxy coatings include
   acid tanks
   chemical reactors
   refinery vessels

3. Vinyl Ester Coatings

Vinyl ester coatings are used when the chemicals are very aggressive. They are very good at resisting corrosion resist acids and solvents and can handle temperatures.
Typical uses for vinyl ester coatings include
   chemical storage tanks
   FGD systems
   industrial process equipment

4. Polyurethane Linings

Polyurethane linings are used when the surface is exposed to both wear and tear and immersion. They are flexible durable. Can handle impact.
Typical uses for polyurethane linings include
    slurry pipelines
   hydro structures
    wastewater systems

Surface Preparation Requirements

To make sure the immersion coating works well the surface has to be prepared. This includes
   blasting to the right standard
  making sure the surface is the right roughness
   making sure the surface is clean, dry and free of contaminants
The environment also has to be right with
    the steel temperature at least 3°C above the dew point
    the relative humidity below 85%
     no visible moisture

Typical Immersion Coating System

A typical immersion coating system has layers:
    a primer of zinc-rich epoxy that is 75 µm thick
    an intermediate layer of high-build epoxy that is 150–250 µm thick
    a topcoat of novolac epoxy that is 200–500 µm thick
The total thickness of the coating is about 400–800 microns depending on how harsh the environment is.

Common Failure Problems

Sometimes immersion coatings can fail. This can happen because of
   blisters from water getting in or the coating not curing properly
    the coating coming off the surface because it was not prepared properly
    holes that let chemicals or water in
   corrosion under the coating because it was damaged or contaminated
    the coating coming off near cathodic protection systems

Inspection & Testing

It is very important to test the immersion coating to make sure it is working properly. This includes tests like
   measuring the thickness of the coating
   checking for holes or gaps in the coating
   testing how the coating sticks to the surface
   measuring the roughness of the surface
   testing for soluble salts
Checking for holes or gaps in the coating is especially important for immersion coatings.

Industry Standards

There are many standards for immersion service coatings, including
   ISO 12944
   NORSOK M-501
  SSPC Standards
   NACE Standards
   Saudi Aramco SAES-H-001
   ASTM Standards

Best Practices for Long Service Life

To make sure the immersion coating lasts a long time it is very important to
   use the right abrasive blasting profile
   keep the environment under control
   follow the manufacturers instructions for curing the coating
   apply the right thickness of coating
  check for holes or gaps in the coating
   inspect the coating between layers
  use qualified people to inspect the coating

Conclusion 

Immersion service coating systems are very important for protecting industrial assets that are exposed to water, chemicals and harsh environments. Choosing the coating system preparing the surface properly and inspecting the coating carefully are all very important for making sure the coating lasts a long time and prevents costly corrosion failures. Immersion service coating systems play a role, in protecting these assets.