Anti Corrosion Coating

nano coating

Protect steel & metal from corrosion and rust

Corrosion, most often rust, is the worst enemy of metal structures and surfaces due to the fact that the oxidation weakens the structure and its properties, as well as negatively affects the aesthetics. The durability of steel and other metal structures is essential especially when the structure is in a critical position; for example supporting a building or other construction. Fortunately, anti corrosion coating can improve the durability.

Anti corrosion coating is crucial in increasing surface durability which contributes to cost efficiency.

As anti corrosion paint and coatings are essential especially in industrial steel protection. We collected the most important “need-to-know” facts, product and price information and application tips to protect your buildings from corrosion.

Due to the beneficial characteristics, the industrial anti corrosion coatings are common for example in the following sectors:

aerospace anti corrosion coating

Aerospace & aviation Anti corrosion

anti corrosion coating power generators

Power generation

anti corrosion coating for railways

Anti Corrosion coating for Railways

anti corrosion coating on steel and concrete bridges

Bridges

anti corrosion coating

General industry

anti corrosion coating in the defense industry

Defense

anti corrosion coating on cars

Automotive


Anti corrosion coatings for steel

Successful corrosion prevention is a sum of design and protective means such as coatings and lubricants. The best anti rust solution for your project is dependent on several factors that we will introduce later on. First, we will however, guide you through the basics of anti-corrosion coatings.

So, how do you prevent corrosion with coatings? 

There are three main coating solutions that are suitable for preventing most types of corrosion.

  • Electrochemical surface treatment
  • Liquid and powder anti corrosion coating 
  • Duplex system

Electrochemical anti rust treatment

Electrochemical surface treatment includes methods where the corrosion sensitive metal is coated with another non-corrosive metal. Galvanizing is the most common anti corrosion surface treatment; a ferrous metal such as steel receives a protective zinc layer. The layer is sometimes called sacrificial due to the fact that under certain circumstances it corrodes instead of the underlying metal.

But which metals are corrosion resistant?

As a rule of thumb, non-ferrous metals, thus metals that do not contain iron, are less sensitive or completely immune to corrosion. Metals such as gold, silver and platinum do not corrode at all, but aluminium and copper oxidate as a result of the atmosphere.

Anti corrosion paint and powder coating

anti corrosion coating powder

Anti corrosive coatings are also available as powders.

Anti rust paints and powders are also a method to stop and prevent corrosion. Their main purpose is to form a barrier between the substrate and surrounding corrosion agents. Powder coatings are becoming more and more popular as industrial anti rust solutions.

There are three main types of anti corrosive paints (and powders):

  • Barrier coatings
  • Fluoropolymer paints
  • Sacrificial layers

Barrier coatings form a barrier between the material and the environment. It is a non-porous solution which guarantees that the metal does not get in touch with the corroding factors. Sacrificial coatings for their part are usually metallic layers which slow down the corrosion of the underlying metal by corroding first. Last but not least, fluoropolymers are also barrier coatings, but they are applied in thick films providing maximum corrosion protection.

We’ll dig deeper into barrier coatings little later…

Duplex system

The duplex system has proven to be the most effective coating solution in terms of anti-corrosion. The term refers to first applying an electrochemical anti rust treatment and afterwards finishing the job with either a liquid anti rust paint or a protective powder coating.

A deeper look into anti corrosion coating

The main purpose of these coatings naturally is protecting metals from corrosion.

However, there’s more to it…

Not only is anti corrosion coating designed for rust prevention but it also has other beneficial properties. The anti rust properties can additionally be combined with other, more specific characteristics such as resistance to bacteria or fungi.

Next to corrosion inhibition, most anti rust paint has the following properties, which can further be modified.

  • Acid- and chemical resistance
  • Protection from weathering
  • Resistance to dirt and other contamination
  • Abrasion resistance

What makes coating anti-corrosive?

Corrosion resistant paint, just like other paints, consist of four main ingredients being binders (resins), pigments, diluents (solvents and thinners) and additives. The anti corrosive properties are provided by the special pigments and additives used in these coatings. The most common and effective corrosion inhibitors are:

  • Red-oxide
  • Zinc chromate
  • Zinc powder
  • Magnesium powder

The different types of resins have unique properties and the coatings are suitable for different environments.

Types of resins in anticorrosion coating

The anti corrosive paint and barrier coatings can contain for example:

Epoxy Resins 
Epoxy finish usually requires two coats of primer, before applying the coating itself. The total DFT (Dry Film Thickness) being 100 to 125 microns. Epoxy resins are tough and abrasion resistant. However, the epoxy coatings are not resistant to UV radiation. They tend to chalk in one or two years. They have however, excellent corrosion resistance to most of the chemicals and solvents. Due to the poor UV resistance, the epoxy coatings are suitable for use in the interior of chemical and fertilizer plants.

Coal tar epoxies
This paint comes either in black or brown colour, as it contains coal tar. Coal tar has excellent water proofing quality and hence is suitable for extensive use there where the structures are under water. They are suitable for use for example in ports and dredging equipment where the corrosion due to saline water is very high.

Polyurethane resins
PU Resins or poly urethane resins make excellent corrosion resistant paints. They are not affected by UV light. They are preferred over epoxy resins in all exterior applications. The composite system could be two coats of epoxy resin primers followed by two coats of PU paints giving a total DFT of 100 to 125 Microns.

Chloro-rubber paints
One more class of resins used in corrosion resistant coatings is the chloro rubber binders. They provide an excellent corrosion resistant coating in a chemical environment. However, being thermoplastic resins, they corrode easily by solvents and cannot withstand higher temperatures.


The best anti rust coating for your project

To define the best anti rust coating for your project, you must ask yourself two questions:

  1. In what kind of environment the project is, thus what kind of corrosion it is likely to experience?
  2. When is the first maintenance of the coating (required durability)?

But how to define the environment?

The international standard ISO 12944, recoginises five different main classes for corrosion. We’ll introduce these later in this article. However, first we will introduce the types of corrosion and suitable coatings for proper prevention.

lack of anti rust treatment under screws


Types of corrosion

Corrosion in general refers to erosion of metals which is caused by prolonged exposure to salt spray, humidity or water. However, metal corrodes also without the presence of these factors if long enough time passes. Anti corrosion paint is designed to prevent rust and other forms of corrosion.

However, you should be aware of the type of corrosion that the surface may experience due to the fact that the prevention methods vary per corrosion type.

Take a look at the following table to get to know the most common types of corrosion!

Corrosion type
Explanation
Protection methods
Uniform attack  Uniform attack corrosion (or uniform corrosion) refers to a situation where the whole surface is under oxidation attack. The corrosion thus, spreads at a uniform rate. Anti rust paint, oil or sealant, electrochemical anti rust solution like galvanizing
Galvanic  Galvanic corrosion is triggered when two metals of different electrode potentials come in contact with each other in presence of an electrolyte such as saltwater. As a result metal ion flow from the more active material to the less active one speeding up the corroding of the more active metal. Barrier coating, electochemical treatment or sacrificial anode
Pitting  Pitting corrosion is a form of galvanic corrosion, in a microscopic scale. It occurs when a tiny part of the metal loses its protective layer, and becomes exposed to corrosive factors.  Anti corrosion coating or cathodic methods
Crevice  Spaces where access to surrounding air or liquid is poor meaning that the fluid can access the space, but cannot exit. This happens often under screws, washers and barnacles. Minimising the tight spaces in design

Now that you know the types, it is time to define which metals may suffer from those and of course, how to appropriately prevent the types from occurring. All that you can find in the table below.

Metal
Possible types of corrosion
Corrosion prevention
Galvanic activity
Stainless steel  Uniform, galvanic, pitting, crevice Cleaning, protective coating or sealant ( anti corrosion coatings for steel)   Low (corrosion form resistant oxide layer)
Iron  Uniform, galvanic, crevice Cleaning, protective coating or sealant, galvanization, anti-rust sol’ns  High
Brass  Uniform attack, stress  Cleaning, protective coating or sealant (usually oil or lacquer), adding tin, aluminum, or arsenic to alloy  Medium
Aluminium  Galvanic, pitting, crevice  Cleaning, protective coating or sealant, anodizing, galvanizing, cathodic protection, electrical insulation  High (corrosion form resistant oxide layer)
Copper  Galvanic, pitting, aesthetic tarnishing  Cleaning, protective coating or sealant, adding nickel to alloy  Low (corrosion form resistant oxide layer, patina)

Anti-corrosion coating products & prices

Regional differences in materials, labor and equipment can all have an impact on overall costs if you want to contract a coating expert. So if you are looking for local prices in the UK or manufacturers in cities like London and Manchester we advice you to request a tailored quote.

So, let’s take a look at  some Anti Corrosion products available in the UK.

Product
Coating type
Price (MSRP)
Packaging
Jotun Jotamastic 90 Surface tolerant and abrasion resistant 2K epoxy coating. Also suitable when surface preparation is not possible £62.57 5 L
Rust-Oleum Mathys Noxyde waterborne 1 pot system for anti corrosion applications. Easy to apply spray coating. £41.15 5 Kg
Rust-Oleum Combi Primer A high quality anti rust primer which is recommended to use under Rust-Oleum Combi Color to ensure longer rust protection on new or rusted steel. £8.63 400 ml

Note that these prices are merely indications, and can vary per anti corrosion coating manufacturer.

Proper anti rust treatment for steel is a multi layer system

Steel has many advantages; unfortunately, immunity to corrosion is not one of them. Anti corrosion coating for steel is thus, essential due to the fact that corrosion weakens steel, reduces its conductivity and makes it look less appealing.

Explanation of corrosion resistant paint

Example of anti corrosion coating system

An appropriate anti corrosion coating can however, eliminate all those issues and extend the life span of steel.

The system of anti rust treatment for steel essentially consists of four steps, and several coating layers:

  • Surface preparation (derusting, blasting etc.)
  • Primer or galvnizing
  • Sealer
  • Undercoat(s)
  • Topcoat (and sealing solution)

Preparing the steel surface to protect from rust

Surface preparation is an essential part of any coating job where success is wished. So, it is also necessary when applying anti rust paint. If you wish to rustproof an already corroding surface, first remove all the rust.

There however, is anti rust paint that is suitable for already corroding surfaces.

After cleaning the surface, abrasive blast cleaning is recommended to let the primer adhere properly. Thus, after blasting the surface, a primer is applied. The primer is the initial protective coating on the surface. Usually an undercoat is applied on top of the primer, to further protect the primer, and so the surface. However, sometimes a sealer layer takes place between primer and undercoat. The last layer is a finishing top coat which seals the surface.

Application methods 

Application methods for industrial anti rust coatings include:

Steel being applied with anti corrosion coating

  • Low pressure spray;
  • Airless spray (also available for 2K systems);
  • Electrostatic spray (for corrosion resistant powder coating);
  • Robot operated spraying techniques (liquid and powder coatings);
  • Curtain coating;
  • Dip coating (fluidised bed application for corrosion resistant powder coating).

Nevertheless, some anti rust paints are also suitable for non professional applications. Those paints are usually applied with brush or roller. Also aerosol sprays are available for rustproofing smaller surfaces.

The British and international standard for corrosion

Especially for industries, it is crucial that the coatings used, meet several standards. In case of anti-corrosion paint the standard is ISO 12944, which is the international standard for corrosion protection of steel structures with protective paint systems. The standard provides guidelines and assists engineers and corrosion experts in creating corrosion protection for structural steel at new construction.  Selecting specifications that comply with ISO 12944 can be beneficial due to the fact that the standard:

  • Guarantees your corrosion protection is suitable for the purpose
  • Helps selecting an anti corrosion coating & paint
  • Provides a meaningful coating design life
  • Is a universally accepted standard

The standard can eventually help you saving in costs due to the fact that it allows you to define which coating you need, eliminating mistakes and bound costs. It also guarantees that your coating is not over qualified thus more expensive.

Back to selecting the best anti corrosion coating…

ISO 12944 divides corrosive environments into five main groups. The required durability for its part can be low (less than 5 years), medium (from 5 to 15 years) or high (more than 15 years).

There are five categories of corrosive environments: As a rule of thumb, the harsher the environment, the more expensive the coating.

ISO 12944 Environment
Description
Examples
C1  Low need for protection Heated buildings, temperature neutral environments such as offices and schools
C2 Low to medium need for protection  Rural areas with low pollution including garages, warehouses and sports halls
C3  Medium need for protection Urban and industrial environments with moderate sulfur dioxide levels including production areas with high humidity such as industrial kitchens, breweries and food processing plants.
C4 Medium to high need for protection Industrial and coastal environments such as harbours, chemical processing plants and other factories
C5I (industrial) High need for protection Industrial high humidity areas with aggressive atmosphere
C5M (maritime) High need for protection Marine, offshore, estuaries and coastal areas with high salinity for example off shore oil platforms.

 


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