Professional guidance to choosing an anti corrosion coating
This is a complete guide to choosing an anti rust coating for steel and other metal structures in a variety of environments. Here you will find a quick introduction to anti corrosion coatings, the corrosion categories by ISO standards and suitable coatings per category.
Anti rust coating acts as a barrier between a metal and its environment, increasing its durability and lifespan. The estimated global cost of metal corrosion damage is billions of dollars. The good news is, a lot of this loss can be prevented by being proactive, and choosing the right anti rust coating from the start.
Corrosion is caused by a chemical reaction between a metal and its environment (water or other fluids), 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 rust coating prevents direct contact between water/fluids and the steel substrate and therefore prevents the corrosion process.
Start by assessing the corrosion risk before choosing an anti rust coating
To determine the right types of anti corrosion coatings for your project, you need to understand the environment and use of the substrate. Particularly 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 Organisation for Standardization. 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 which are constantly exposed to moisture, but also for small pipes that are equally exposed.
- C1 – very low corrosion risk: Heated buildings with clean air, interiors only.
Suitable for: offices, schools, hotels, shops and other heated premises.
- C2 – low corrosion risk: Unheated buildings, rural areas.
Suitable for: storage facilities, sports halls, garages, barns and other unheated buildings.
- C3 – moderate 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.
- C5 – very 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).
The anti corrosion coatings per category (C1-C5)
Once you have identified your environment, you can identify the right anti rust treatment for your project and the right anti rust coating specification to protect it for years to come. Choosing the most suitable anti rust coating allows you to avoid overspending on unnecessary degrees of protection or simply prevents you making the wrong choice.
Anti corrosion coating types can be divided into the following categories:
- BARRIER COATINGS (C1 – C3) – non-porous anti rust coatings designed to prevent corrosive factors coming into contact with the substrate.
For example: powder coating, polyurethane paint, chloro rubber paints, Teflon coatings, nano coatings.
- INHIBITOR COATINGS (C1 – C4) – anti rust treatment which releases a chemical that 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.
- CATHODIC PROTECTION (C3 – C5) – metal-rich anti rust coating for steel 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.
A duplex system for the best corrosion resistance for steel
When hot dip galvanising is used together with a topcoat of anti corrosion paint or powder it is known as a Duplex System. The duplex systems are applied as anti rust coating for steel and occasionally other metals. This type of anti rust treatment provides multiple types of protection and the longest-lasting results. Each layer needs to be compatible in order for the system to work effectively. Duplex anti rust coating systems are especially suitable for corrosion categories C3 to C5.
Anti rust paint for light corrosion resistance & small substrates
For smaller substrates or do it yourself application up to category C2, painting is also an option. There are also small anti corrosion spray paint cans available for this purpose. An anti corrosion coating spray can be described as an ultra thin fluid film compound which you can spray on any steel or metal surface. In spray form it can protect for up to a year. But keep in mind that more exposed areas that are getting constant abuse from rain and salt will need spraying regularly. With anti rust paint, more long lasting results can be accomplished depending on the coating system you choose. For the best result always opt for a two component anti rust coating with corrosion inhibitor additives, for example a zinc rich epoxy coating.
Anti rust coating products for different environments
Here is a selection of products on the market to give you a rough guide as to the price of anti corrosion paint. Keep in mind that for categories C4 and C5 it is not recommended to apply the anti corrosion coatings yourself. Please search out a specialist in that case.
|PRODUCT||Anti corrosion coating TYPE||Corrosion Category|
|Jotun Jotamastic 90||Barrier coating: Epoxy coating for above and below water, on concrete or steel, with abrasion and chemical resistance.||C1 – C3|
|Jotun Barrier 90||Inhibitor coating: Zinc-rich epoxy containing 90% zinc. Suitable for above water and on steel, with abrasion and water resistance.||C1 – C4|
|Hempel Galvosil||Cathodic protection: two-component, solvent-borne, self-curing, inorganic zinc silicate with outstanding resistance against weathering and abrasion.||C3 – C4|
|Hempel Hempadur||Galvanising coating: two-component, epoxy based. It cures to a flexible, well-adhering coating with good abrasion and impact resistance. Contains zinc phosphate||C3 – C4|
|Ultrimax 1||Inhibitor coating: Contains zinc phosphate anti-corrosive properties and a high volume of solids.||C1 – C3|
Find corrosion resistant coating specialists in New Zealand
If you are looking for a professional company to apply the 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 pricing is usually calculated by size or surface area. Regional differences in materials, labour, and equipment can all have an impact on overall costs when contracting an anti rust coating expert.
In New New Zealand the anti rust coating specialists include for example Modern Maintenance Products located in Auckland; this company is dedicated to supplying and applying anti corrosion products. If you are need of more information on anti corrosion coatings or specialists near you, do not hesitate to contact us. Our experts are happy to use our extensive network to find you the right product and contractor!
Below we provide a list of anti rust coating manufacturers located in New Zealand.
|Anti rust coating manufacturer||Address|
|Altex Coatings Ltd||91-111 Oropi Road , Greerton, Tauranga 3112|
|CRC Industries||10 Highbrook Dr, East Tamaki, Auckland 2013|
|Protective Paints||14 Arwen Pl, East Tamaki, Auckland 2013|