There are many reasons why steel surfaces are treated, from making them more attractive through to protecting them against scratching, peeling, extreme weather and corrosion. Here we take a brief look at some of the most common steel surface treatments utilised nowadays as well as a few of their many benefits.
The secret to choosing the right steel surface treatment is recognising the level of corrosive threat and balancing any aesthetic concerns as well.
Why steel surface treatment may be required
All steel will eventually corrode if not treated properly. This will not only ruin its aesthetic but also affect its structural integrity.
There are many types of corrosion. Here are a few of the most common:
• Uniform attack corrosion – Also known as general attack corrosion, this results in the deterioration of the entire exposed surface of the steel. This kind of corrosion is caused by a chemical or electrochemical reaction that results in the deterioration of the entire exposed surface of the steel. The best way to protect against uniform attack corrosion is to establish a barrier between the steel and the malicious agents
• Galvanic corrosion – Galvanic corrosion, or dissimilar metal corrosion, occurs when steel comes into contact with another metal in a corrosive electrolyte. The best way to avoid this is make sure different metals do not have direct contact
• Pitting corrosion – Pitting corrosion occurs when localised areas of steel lose their protective layer. This area becomes anodic, while part of the remaining metal becomes cathodic, producing a localised galvanic reaction. You can avoid this by being particularly diligent with your steel and to re-apply protective coatings regularly, or use cathodic protection.
• Crevice corrosion – Similar to pitting, crevice corrosion is localised, generally in a stagnant microenvironment where acidic conditions, or a depletion of oxygen in a crevice can lead to corrosion. The best way to protect your steel from crevice corrosion is to eliminate tight gaps in steel construction.
Zinc phosphate priming
Steel surfaces can be painted with specially formulated primers in order to improve corrosion resistance as well as boost their visual appeal, with one of the most popular applications being zinc phosphate priming. Zinc phosphate is an inorganic chemical compound that can provide active or inhibitive corrosion resistance to low-alloy and carbon steel and zinc primer has been used in everything from construction to ship building to the automotive industry.
The power coating, or chemical coating, technique uses electrostatic or compressed air to apply a specially formulated powdered material to the steel surface, following which it is melted to form a smooth protective film. Steel treated in this way is not only protected against corrosion and UV damage, it is also highly resistant to peeling, scratching and cracking. Because powdered chemical coatings have no liquid component thicker protective coatings can be applied and they also tend to emit fewer volatile organic compounds.
This galvanization method can be used on steel of all shapes and sizes and involves immersing the steel in a bath of molten zinc at temperatures up to 450°C. When the zinc coated steel is removed from the bath, the zinc reacts with the oxygen and carbon dioxide in the atmosphere, the end result being a strong, dull material. Steel has been hot dipped in this way is highly protected against corrosion as well as extreme weather conditions and this is a particularly popular approach for pipe related applications.
Zinc spray metallizing
While it doesn’t provide quite the same protection as hot dip galvanising, the zinc spray metallising technique is highly effective against corrosion and is popular for its smooth finish. First the steel is shot blasted to create a roughened surface then the zinc spray is applied almost immediately, resulting in a solid bond being formed between the zinc and the steel. Because this is a ‘cold process’ there is no risk of distorting the metal, making it ideal for use on ornate metal components such as railings and fences.
Choosing the right treatment
The secret to choosing the right steel surface treatment is recognising the level of corrosive threat and balancing any aesthetic concerns as well. Whether the steel will be indoors or outdoors and the temperatures it will be exposed to will make a considerable difference, as will the levels of salinity, humidity and pollution in the atmosphere.
Few materials can compare with the strength, durability and versatility that you get from steel; however, unless those surfaces are adequately protected your steel’s performance will be seriously undermined. If you need quality steel that is fabricated to suit your unique needs, contact Steel Fabrication Services today. Our team of expert structural steel fabricators have the experience and knowledge to answer any of your questions and will ensure that you find the best solution to suit your needs. To contact us today, simply call, fax, email or drop by our Brookvale location.