Overview
- Zinc is a popular coating that provides a metallic barrier to pipes, protecting them from corrosion by acting as a sacrificial layer.
- Epoxy is a highly-used anti-rust coating that seals out oxygen from metal, offering protection against corrosive liquids and high temperatures.
- Polyurethane is a hardwearing resin that provides chemical and solvent resistance, enhancing the durability of metal pipes.
- Paint is a common and economical anti-rust solution that acts as a barrier against water and oxygen.
Corrosion happens due to the combination of metal and oxygen or other chemicals. It is the slow deterioration of the material. That is why it is the biggest issue when using any steel pipes. It’s due to the fact metal is vulnerable to rusting, affecting the safety and durability of your project.
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Fortunately, it can be easily avoided to ensure the longevity of your building. Let’s look at the different types of anti-rust coatings for your metal pipes. From zinc to paint, let’s discover the four protective layers to ensure the optimal performance of our materials.
Zinc is a popular coating for various steel materials. It is a component of brass that provides a strong metallic barrier to your pipes. As an important component in construction, its advantage is increasing the durability of your projects.
Mainly zinc is used to combat corrosion. As a layer, it protects your metal materials from the process of oxidation. It acts as a sacrificial barrier because when corrosion occurs, it does not affect the material but the coating itself. So, when you see your metal pipes rusting, know that it is the zinc that it targets first before your pipes. This gives you time to respond accordingly to the issue.
Often, zinc is layered to your steel resources through a process of galvanizing. Galvanization involves hot-dipping your pipes into molten zinc to coat them. The result of this is your reliable galvanized iron pipes.
The second type of anti-rust coating for your pipes is epoxy. It is a combination of resin and hardener, focusing on sealing out oxygen from the metal. As a highly-used steel coating, it is often found in projects in the marine industry since it can cure underwater or on damp surfaces with minimal surface preparation.
Apart from anti-rust qualities, epoxy coatings have many advantages. It offers protection against corrosive liquids, turbulence, and maximum temperatures. Moreover, it lasts for a very long time. This will help you avoid any further maintenance for your steel pipes.
Epoxy coatings come in three different categories. They are the water-based, solvent-based, and solvent-free coatings. Each offers its distinct considerations. In choosing the best option for you, a proper understanding of your unique specifications is required.
Like epoxy, polyurethane is a hardwearing resin solution to this issue. It consists of two main components, the isocyanate groups and hydroxyl groups. The former is a designation of the nitrogen, carbon, and oxygen atoms. The latter refers to the group of hydrogen and oxygen atoms. The combination of these two parts is polyurethane resin itself.
As a protective layer, polyurethane is an excellent choice. It does not only work to combat corrosion but there are also other qualities it offers. When you coat your metal pipes with polyurethane, it gives you resistance against chemicals and solvents. They are acid-resistant and can enhance the longevity of your piping systems.
In addition to that, polyurethane is also an economical coating. This means that it is easy to apply. After proper surface preparation and application, they dry or cure very quickly.
Paint is the most common solution to prevent pipe rust. Often found in most households, it is a cheap process of protecting your metal materials.
This coating comes in three major components. They are binder, pigment and extender, and solvent. The solvent is simply for application aid while the first two are the final dry paint film. When applied on the surface of your metal pipes, it acts as a barrier that stops water and oxygen from reaching the material.
While it can fight corrosion, it may not be the most durable in the long term. However, there are specialized paints that focus on your specific needs. Some paint manufacturers develop anti-rust paints for any metal type. Using these rather than common household paint will help you prevent damage issues.
Selecting a suitable anti-corrosion coating is essential. This is to ensure the reliability of your pipes whether they are used for structural or transportation needs. However, in your search for the appropriate coating, it is important to note that various coatings offer their distinct advantages and considerations.
With Supreme Pipes, big decisions like this are not overwhelming. We understand the importance of steel pipes in various applications. That is why we make sure we give you not only the right materials but the right advance. So, to start your anti-rust journey, contact us today and, together, let’s optimize your pipe materials!
Properly managing and mitigating pipe corrosion will help minimize the risk of damage to the pipeline’s integrity and help maintain its reliability and longevity while transporting everything from natural gas, liquid petroleum, biofuels, water, sewage, etc.
Without corrosion protection, the pipes will lose mechanical strength and develop exterior holes and cracks that can lead to breaks, floods, and billions of dollars annually in maintenance and repairs. Preventing pipe corrosion will also protect the safety and health of the nearby communities, ecosystem, and pipeline workers.
Pipeline corrosion prevention must protect against degradation and conduct cathodic protection currents should the coating become damaged or disbond; both features of Polyguard’s long-lasting RD-6® COATING SYSTEMS.
Pipe corrosion happens when the metal surface deteriorates due to an oxidation-reduction or redox reaction. Higher temperatures, salts, and acids will accelerate corrosion. The process of corrosion requires four elements:
All corrosion types deteriorate refined metal piping due to chemical interactions that naturally convert the metal to a more chemically stable form, like metal oxide (rust). However, each corrosion type needs particular protection methods to ensure the pipe's long-term integrity:
Galvanic corrosion involves unlike metals of different corrosion resistance electrically connecting, which causes the anode area on the metal to deteriorate.
Preventing galvanic corrosion requires placing insulation between the two metals and using a combination of metals close in the galvanic series. Applying a non-shielding coating to the cathodic surface of the metal can also help stop galvanic corrosion.
Several situations can lead to pitting corrosion: mechanical damage to the protective coating, pipe and surface material defects, and attack by aggressive chemical species, like chlorides. All can lead to dangerous, localized deterioration on a limited surface space that can create punctures and pits on a pipe's surface.
To stop pitting corrosion, choose a suitable pipe material for the service environment, considering the reactant’s chemical concentration (pitting resistance) and temperature. In addition, protect the cathodic and anodic with a sufficient coating to withstand the environment.
Uniform pipe corrosion causes consistent material loss along the pipe's surface, which could eventually lead to continuous thinning of the solid structure.
Preventing uniform pipe corrosion requires choosing an adequate piping material combined with corrosion protection methods like cathodic protection and surface coatings.
Selective leaching (graphitic corrosion) happens when a noble metal and a more reactive element create an alloy, which causes a loss of the reactive component from the pipe's surface, and reduces the pipe's strength.
Contact us to discuss your requirements of Anti-Corrosion Steel Pipe. Our experienced sales team can help you identify the options that best suit your needs.
Adding aluminum or tin can help protect against leaching.
Stress corrosion cracking (fatigue corrosion) results from the growth of pre-existing cracks, causing the failure of metal pipes that surpass threshold stress levels under tensile stress, especially at high temperatures.
Keeping loads below the threshold stress levels can help stop stress corrosion cracking.
Crevice corrosion happens when oxygen-starved surfaces of a pipe's crevices or joints turn into the anode in an electrochemical reaction.
Using welded joints instead of riveted joints can help prevent crevice corrosion. Areas with step-downs or reductions in wall thickness can present spaces of concern for crevice corrosion and require attention when applying the anti-corrosion coating.
Stray currents (DC and AC) flowing through pipelines can cause stray current corrosion, which causes localized pinholes and pitting on metal surfaces at the exact points where stray currents exit the surface. Stray currents can come from cathodic protection, electric railways, welding machines, buried lines, or high overhead voltage.
You can lessen stray current corrosion by bypassing stray current to an earthing station or managing electricity leakages through bonds to other structures.
Grains comprise the microstructure of metals and alloys, and are separated by grain boundaries. Intergranular corrosion occurs along the grain boundaries or immediately adjacent to grain boundaries. Impurities (chemicals) precipitating on the grain boundaries often lower the area's corrosion resistance.
Using extra-low carbon stainless steel materials can help stop intergranular deterioration.
Cavitation and erosion-corrosion in a pipe occur when the fluid's working pressure is less than its vapor pressure. It causes vapor bubbles and pockets to form, which causes the pipe's internal surface to break and leads to erosion-corrosion.
Areas of a pipe particularly susceptible to erosion-corrosion include the discharge pipes, pump suctions, tees, elbows, expansions, fitments at heat exchangers, and valve seats.
There are several ways to prevent cavitation and erosion corrosion:
High-temperature corrosion occurs under extreme temperatures (often above 400℃ (750℉)). Chemical attacks from gasses or molten metals that contain specific contaminants will produce high-temperature corrosion.
The oil and gas industries often favor using alloy pipes to prevent high-temperature corrosion. Alloy pipes comprise two or more metallic elements, like steel and chromium, which create greater strength and corrosion resistance.
External surface corrosion on a steel pipe happens due to environmental conditions that cause an electrochemical interaction between the pipeline's exterior and the adjacent water, air, and soil.
The first line of defense in stopping external pipeline corrosion involves removing one of the four elements required for corrosion - cathodes, anode, metallic path, and electrolyte. A coating system can protect the pipeline from the electrolyte (often water) by acting as a barrier that breaks the corrosion cycle. In addition, some barrier coatings use sacrificial or inhibitive pigments that cause passivation or a sacrificial anode to form defects in the coating.
Cathodic protection (CP) currents offer a second line of defense that protect the pipe if the coating becomes damaged, which creates a corrosion-prone space. CP allows the cathodic current to reach the pipeline’s disbonded areas to raise the water’s pH between the pipe and disbonded coating to 9 or above - a value that does not support corrosion.
Polyguard Pipeline Coating products protect the pipelines' integrity by minimizing corrosion and providing impact, chemical, temperature, and ultraviolet (UV) resistance, strong adhesion, and straightforward application.
The non-shielding, anti-corrosion Polyguard RD-6 Coating System can be used on submerged and buried line pipe, rehabilitation, and new construction girth welds (operating at no more than 145°F (63°C)).
The Polyguard RD-6® coating system comprises a tightly woven, robust polypropylene geotextile fabric that bonds to the coating on the pipe's exterior surface to furnish non-shielding properties, low elongation, and high breaking strength. The woven geotextile polypropylene backing produces tension and compression during RD-6® application, which ensures its lasting performance.
We also offer coatings and outer wrap products for high temperatures, above-ground, and larger pipe diameters:
RD-6® COATING SYSTEM’s non-shielding design, with its geotextile backing’s open weave, allows for the passage of corrosion protection currents to damaged or compromised areas of the coating, to elevate the pH of the electrolyte in the space to above 9, which will not support corrosion.
Soil-stress-resistant RD-6® limits disbondment from the pipe, even with less-than-perfect surface preparation.
Polyguard manufactures RD-6® coating in rolls for straightforward application using a Polyguard-approved machine like the Wrapster or power-operated machine.
The Polyguard Wrapster has two spindles: one offers tension when applying the RD-6® coating to the pipe. The other spool releases the liner when applying. You can also apply RD-6® manually without the Wrapster if you apply tension consistently during the application.
In addition, RD-6® does not require curing. It includes a silicone-coated release liner to prevent the layers from adhering to one another and help in the application process.
The dependable and verified POLYGUARD RD-6® Coating System has protected pipes for over thirty years from external corrosion and stress corrosion cracking. The non-shielding RD-6® Coating System offers superior, long-lasting pipe corrosion prevention and provides cathodic protection currents during disbondment.
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