anti corrosion coating failure on bolts

Anti corrosion coating prevents rust on steel and other ferrous metals

Anti corrosion coating acts as a barrier between a metal (usually steel) and its environment, and increases its durability and lifespan. The roughly estimated global cost of metal corrosion damage is trillions of rials. The good news is, a lot of this loss can be prevented by being proactive, and making the right choice of anti corrosion coating from the start.

To determine the best rust proof metal coating for your project, it is important to factor in the environment and type of metal. Whether corrosion is due to moisture, chemicals, salt spray, prolonged exposure to sunlight or oxidation, corrosion resistant coating for steel and metal can help protect the substrate from the elements.

Rust proof metal coating is not just one type of paint

Rust that could have been prevented with anti corrosion coating

Prolonged exposure to UV radiation leads to severe damage which could be prevented by an anti corrosion coating

Anti rust coating is essentially a collective name for various types of coatings that protect a metal substrate from corrosion. An anti corrosion coating can do more than just protect from corrosion, and its multi-functional nature means that it is possible to find the exact coating your project requires. Corrosion is caused by a chemical reaction between a metal and its environment, typically producing an oxide or a salt of the original metal. The long and the short of it is the metal is weakened, as is the structure it creates. An anti corrosion paint prevents direct contact between water, fluids or another hazard (UV radiation) and the steel substrate and therefore prevents or slows down the corrosion process.

In general anti corrosion coating is suitable for almost any type of steel and metal, and has the following 5 benefits:

  1. Fends off fungi, algae, and moss
  2. Weather protection against acid rain, salt water, ice and so on
  3. Chemical resistance
  4. Repels water & other fluids (in case of barrier coatings)
  5. Depending on the type of anti-corrosion coating you opt for: anti fouling, non slip or self cleaning properties

Identify the corrosion category to pick the best anti corrosion coating

To determine the most suitable anti corrosive coating for your project, you need to understand the environment and use of the substrate; especially its exposure to water, moisture, and other aggressive substances that might be present in the environment. The corrosivity of certain atmospheres has been classified and standardised by the International Organization for Standardization (ISO). The standard divides the degree of corrosivity into 5 categories , C1 to C5, in order of increasing corrosivity. To find the right anti-corrosion coating, you need to know how corrosive the environment will be. For example, a coating at C5M level is intended for offshore constructions an pipelines which are constantly exposed to moisture, but also for small pipes that are equally exposed. An example of such applications is the Al Ain – Fujairah pipeline, as part of the Dolphin Gas Project where Ras Laffan is in a key position, that exports natural gas from Qatar to Oman; the pipe is 182 kilometers long and is protected with rust proof coating all the way.

  • C1 very low corrosion risk: Heated buildings with clean air, interiors only.
    Suitable for: offices, schools, hotels, shops and other heated premises.
  • C2low corrosion risk: Unheated buildings, rural areas.
    Suitable for: storage facilities, sports halls, garages, barns and other unheated buildings.
  • C3moderate corrosion risk: Buildings with high humidity, urban and industrial areas.
    Suitable for: laundries, breweries, kitchens, food processing sites and other buildings with moderate humidity.
  • C4 high corrosion risk: Chemical manufacturers and swimming baths, industrial and coastal areas.
    Suitable for: industrial buildings, chemical plants, swimming pools, ports, and ship- and boatyards.
  • C5very high corrosion risk: Buildings with almost permanent condensation, offshore and industrial areas.
    Suitable for: Water pipes and other industrial applications (C5I – industrial). Offshore and maritime constructions (C5M – marine).

Once you have determined the corrosivity of your environment, you can determine the right coating systems for your project and the right anti corrosive coating specification to protect it for years to come. Following these guidelines will allow you to pick appropriate anti rust coatings, allowing you to avoid overspending on unnecessary degrees of protection or simply making the wrong choice.

The 3 options for industrial anti rust coatings

Anti corrosion coatings can be divided into three categories:

  1. Barrier coatings (C1 – C3) – non-porous coatings (anti corrosion paint) designed to prevent corrosive factors coming into contact with the substrate.
    For example: powder coating, polyurethane paint, chloro rubber paints, Teflon coatings, nano coatings.
  2. Inhibitor coatings (C1 – C4) – release a chemical which interferes with the electrolyte and stops the corrosion process.
    For example: all oil based coatings with corrosion inhibitor additives such as zinc, aluminum, zinc oxide and so on.
  3. Cathodic protection with galvanic coatings (C3 – C5) – metal-rich coatings which provide a sacrificial layer. Prevents corrosion by providing a more easily corroded metal (such as zinc) to be the anode to the protected metal’s cathode. Also called the sacrificial anode, this metal will corrode instead of the protected metal.
    For example: hot dip galvanizing which provides steel (cathode) with a layer of zinc (anode).

Keep in mind that for categories C4 and C5 it is not recommended to apply the coating yourself. Please search out a specialist in that case.

Apply anti rust coating by spraying or dipping

The two most common methods for applying an industrial grade anti corrosion coating for steel are hot dip galvanising and thermal (metal) spraying. Barrier coatings and corrosion inhibitor coatings can also be applied by spraying or dipping.

Hot Dipping is the process of immersing a metal in a bath of metal, often molten zinc,(or a polymer) in order to form a coating. The liquid metal bonds to the substrate and forms an alloy, which is then coated in zinc as it is removed from the bath. Hot dip galvanising uses the principle of cathodic protection, as the zinc coating acts as an anode to its substrate.

Thermal spraying applies zinc or aluminium to a substrate by taking the metal in the form of a powder or wire and feeding it into a special spray gun. The metal melts within the gun and can then be sprayed onto the substrate. It does not alloy, but instead works by coating the surface in overlapping metal platelets.

Duplex System creates the best anti corrosion coating

When hot dip galvanising is used together with a top coat of anti corrosion paint or powder it is known as a Duplex System.

A duplex system provides multiple types of protection and the longest-lasting results. Each layer with anti corrosive properties needs to be compatible in order to allow the system to work optimally. It is particularly suitable for corrosion categories C3 to C5 and looks like this:

  • Surface preparation: derusting, blasting, removing grease, oil, dirt for optimum adherence.
  • Primer: hot dip galvanisation OR applying an inhibitor coating primer depending on the coating system of your choice.
  • Sealer: To seal the anti corrosion coating. Often epoxy based.
  • Intermediate coat: there may be several layers necessary for optimum protection, depending on the corrosion category.
  • Finishing coat: provides appearance and surface resistance, often first line of defence.

Anti rust coating spray and paint for small projects

For smaller substrates or do-it-yourself application up to category C2, painting at home is also an option to consider. There are also small anti corrosion coating spray cans available for this purpose. An anti corrosion spray can be described as an ultra thin fluid film compound which you can spray on any steel or other metal surface. In spray form it can protect for up to a year. Keep in mind that more exposed areas which are getting constant abuse from rain and salt will need spraying regularly. In paint form, longer lasting results can be accomplished depending on the coating system you choose. For the best result always opt for a two component coating with corrosion inhibitor additives, for example a zinc rich epoxy paint or primer.

Find an anti corrosion coating expert in Qatar

If you are looking for a professional company to apply anti corrosion coating for you, it’s important to understand how prices are established before you request a quote. Different coating processes use different methods to calculate the cost of professional application. Hot dip galvanising prices are usually calculated by weight. The galvaniser will quote a price per tonne, and then use the weight of your steelwork after galvanising to calculate the final cost. Unlike galvanising, powder coating prices tend to be calculated by size or surface area.

Regional differences in materials, labour, and equipment can all have an impact on overall costs when contracting a coating expert. If you want to receive a custom made quote, please contact us.

Here are a few examples of local anti-corrosion specialists in Qatar:

Anti corrosion coating companyAddressSpecialization
Hitech Projects56 Salwa Rd, Doha 201646, QatarApplication of industrial anti rust paints
HertelOffice 202, 2nd Flr, Bldg 141, Thani Bin Jassim St, GharafaApplication of industrial anti rust paints
Hempel Paints Qatar WLLSt 16, Gate 96, Salwa Ind AreaDistribution of industrial anti corrosion coatings
Henkel Polybit Sh Eid Bin Mohd Bldg, Frij Bin Mahmoud, Al sadd, Doha Manufacture of industrial and offshore corrosion resistant coatings
Petrogulf WLL11th-Flr. Almana Business Tower, C-Ring Road, Doha, QatarApplication of industrial and offshore anti corrosion paints

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