Aluminum is a metal (nonferrous). Corrosion occurs when the metal surface is oxidized due to contact with the environment, leading to the degradation of metal properties. Aluminum is abundant on the earth, In this article we will discuss best corrosion inhibitor for aluminium, what causes aluminium to corrode, can you remove corrosion from aluminium, is aluminium anticorrosion and corrosion inhibitor manufacturers in India.
Rust vs corrosion.
When we talk about metal degradation, two different terms come to mind, rust and corrosion. Understanding these two processes is essential to finding an excellent solution to overcome corrosion. At the beginning of my article, I stated, “Aluminum is a metal (nonferrous). To know rust vs. corrosion, you should know what ferrous and nonferrous metals are. Ferrous metal contains iron, but nonferrous metal does not contain iron or is present in a very tiny quantity. Henceforth, as Aluminum does not contain iron, it is a nonferrous metal.
Now, it is easier for me to explain rust. Rusting is a specific process that occurs only in iron or steel. Steel is a ferrous metal that contains iron. When iron in steel reacts with oxygen in the presence of moisture or water, it forms iron oxide, a reddish-brown coating (rust) that appears on the surface. The chemical formula for rust is Fe2O3.nH2O. The rust occurs in the form of flakes, which can tumble down quickly, generating a fresh metal surface for continuing the corrosion process.
On the other hand, Aluminum has a stronger affinity for oxygen than ferrous metal. When Aluminum reacts with the environment in the presence of oxygen or moisture, it forms aluminum oxide instead of iron oxide. Rather than flakes forming, aluminum (aluminum oxide) forms a thin, protective, whitish surface color where all aluminum atoms bond with oxygen to stop the corrosion further. However, if this protective layer is damaged, severe forms of corrosion occur in the form of pits, dull or rough appearance on the surface. In this article, we are also
going to discuss types of aluminum corrosion.
Corrosion inhibitor for aluminium.
Corrosion inhibitor for Aluminum is used to protect the aluminum surface from oxidation and corrosion. Aluminum is prone to corrosion in seawater or polluted air environments. While choosing the corrosion inhibitor for Aluminum, always keep in mind environmental conditions, application components, and the desired degree of corrosion protection. Here are some aluminum corrosion inhibitors.
Phoshate-based inhibitors.
These inhibitors work either by applying them as a primer coating or by coating them as a conversion coating on an aluminum surface. Zinc phosphate and sodium hexametaphosphate (SHMP)are the most commonly used phosphate-based inhibitors.
Zinc phosphate.
Primer coating.
Zinc phosphate is an inorganic compound of an off-white color. It is non-toxic, compatible with most media, and has good corrosion-resistant properties. It is found naturally as the mineral hopeite. BS 5493 recommends that the zinc phosphate percentage in primer formulation be at least 40%. The primer coating utilizes zinc phosphate as a corrosion inhibitor pigment in two-pack epoxy paint, chlorinated epoxy ester systems, etc.
The inclusion of zinc phosphate in the undercoat creates a dense form of pigment packing, which creates a physical barrier for moisture and inhibits the oxidation process.
Rather than protecting against corrosion, zinc phosphate also enhanced the adhesion of subsequent coating layers, such as undercoat and topcoat.
Conversion coating.
Zinc phosphate is applied to the aluminum surface as a conversion coating. In this method, the aluminum substrate is treated with a solution containing zinc phosphate, which reacts with the aluminum surface to form a thin layer of adherent film. In addition to corrosion protection, this coating enhances the adhesion of subsequent layers of coating, such as undercoat and topcoat. These coatings are mostly used in military and defense applications.
Pretreatment for painting.
In many industrial processes, a zinc phosphate solution is used as part of the pretreatment process before painting starts. This pretreatment process removes dirt, contaminants, small debris, and moisture from the aluminum surfaces and helps reduce corrosion protection.
Rust converter.
Zinc phosphate is applied to Aluminum in the form of a solution. This solution is applied by brush, spraying, or dipping. The zinc phosphate reacts with aluminum, particularly with rust, forming a protective layer of zinc phosphate compound on the metal surface.
hexametaphosphate (SHMP)
This inhibitor prevents corrosive agents such as water, moisture, salt, or oxygen from reaching the aluminum surface. SHMP is a hexamer of composition (NaPO3)6 . It has a cyclic structure, with six phosphate units linked together. It is a solid, crystalline white powder.
A straightforward chemical reaction presentation of SHMP with Aluminum is as follows.
Aluminum (Al)+Sodium Hexametaphosphate (SHMP)→Protective Barrier.
PH buffering agent.
Sometimes, SHMP acts as a pH buffering agent, adjusting the pH of the solution. As we all know, the corrosion process is accelerated in an acidic environment. Henceforth, SHMP drives the acidic or alkaline solution to a specific pH state and stops further change in pH. In this way, SHMP mitigates the risk of corrosion.
Solubility.
Due to its high solubility in water, SHMP can be smoothly used in an aqueous solution to apply to aluminum surfaces for corrosion prevention, and it has a high coverage area.
Application.
SHMP has applications in water treatment, metal cleaning, and surface treatment on aluminum substrates. It is also used as a corrosion inhibitor in water distribution equipment, pipes, tanks, etc.
Enviornmental concern.
Extreme use of SHMP causes eutrophication in aquatic ecosystems, boosting the growth of nitrogen and phosphorus, on which algae is fed and spread, turning water green. When the algae is dead, the decomposition process starts, using a high amount of oxygen. Due to inadequate oxygen supply, fish and other aquatic animals start dying, which is not acceptable.
Henceforth, SHMP can be utilized to prevent the corrosion on aluminum parts only careful handling, proportionate use, and environmental concern with the high use of that should be
considered.
Chromate -based inhibitor.
Chromate conversion coatings are mainly used to prevent corrosion on Aluminum. Here are some common chromate-based inhibitors.
Chromate conversion coating.
In this type of coating, the metal surface is treated with a solution containing a chromate compound (chromic acid, chromic salt). The solution reacts with Aluminum to form a thin chromate conversion coating that consists of chromium oxide/hydroxide compounds, which are tightly adhered to the aluminum surface and prevent the entry of moisture, salt, etc. Immersion or spraying is used to apply the solution on a metal substrate. Before the application starts, the aluminum surface should be dirt-free and greased.
Chromate primers.
Chromate-based primers are applied as a base coat to Aluminum. The base coat increases the adhesion of subsequent paint layers on the aluminum surface. Chromate primers are primers in which hexavalent chromium compounds, like zinc, are present.
Chromate sealers.
Chromate sealers are applied over the chromate conversion coating to prevent corrosion and increase the durability of the paint. These seal the pores in the chromate conversion coating, reducing the permeability of moisture and corrosive agents to the aluminum surface.
Chromate additives.
Chromate additives can also be used as corrosion inhibitors for Aluminum.
Chromic acid (CrO3).
Chromate additives can also be used as corrosion inhibitors for Aluminum.
Chromic acid (CrO3) is the primary source of chromate ions used in chromate conversion coatings. It reacts with Aluminum to form a thin layer of chromium oxide, protecting it from corrosion.
Sodium chromate (Na2CrO4).
Sodium chromate is another example of a chromate compound used as an additive in aluminum surface treatment. It participates in the formation of chromate conversion coating, which helps to inhibit corrosion on aluminum surfaces.
Potassium chromate (K2CrO4).
Potassium chromate is another example of a chromate additive for Aluminum. It reacts with Aluminum to form chromium oxide, which protects the Aluminum from corrosion.
Chromate conversion coating solutions.
These solutions usually mix chromate compounds like chromic acid, sodium chromate, or potassium chromate with other chemicals to create a protective chromate coating on Aluminum surfaces.
Chromate Passivators.
Chromate passivation enhances the corrosion resistance of chromate conversion coating on Aluminum. They may contain compounds such as benzotriazole or molybdate, which help to improve the durability and performance of the coating.
Organic Inhibitors.
Aluminum is highly corrosion resistant to the atmosphere and in aqueous solutions due to the formation of an oxide layer, which does not allow further oxidation of the metal. However, aluminum becomes highly susceptible to corrosion in specific environments, such as in acidic mediums. Most organic compounds used as corrosion inhibitors were tested in an HCl solution, which causes significant corrosion and, therefore, needs to be inhibited.
Before applying the organic coating, the Aluminium surface should be cleaned and prepared. The process consists of degreasing the surface, removing the existing oxide layer, and applying the base layer and the primer: the surface cleaning and treatment influence these coatings’
adhesion and anticorrosion properties. The final layer is selected depending on the environmental conditions in which the product will be used.
Organic compounds act as corrosion inhibitors for Aluminum. In particular, acidic solutions, HCl and H2SO4, are widely used in several processes, including acid cleaning, chemical or electrochemical etching, acid pickling, etc.
Organic acids.
Organic acids such as citric acid, acetic acid (vinegar), and tartaric acid can act as corrosion inhibitors for Aluminum. These acids form a protective layer on Aluminum to prevent corrosion by blocking access to corrosive elements.
Amines.
Amines, such as ethanolamine and octadecylamine, are frequently used as corrosion inhibitors or Aluminum. These compounds adsorb to the aluminum surface and create a thin protective layer. This layer stops the metal from dissolving too quickly, which helps prevent corrosion.
Organic polymers.
Polymers contain carbon atoms in their backbone. Certain organic polymers, such as polyethylene glycol (PEG) and polyvinyl alcohol (PVA), can also act as corrosion inhibitors for aluminum.
Organic phosphates.
These compounds adsorb to the aluminum surface and mix with the metal to make a protective layer. This layer stops corrosion from happening.
Organic surfactants.
Certain organic surfactants, such as alkyl sulfates and alkylamines, can also act as corrosion inhibitors for Aluminum. By adsorbing on an aluminum surface, they form a protective film that creates a barrier between the metal surface and corrosive elements.
Silicate based corrosion inhibitor.
Silicate is frequently used as a water-based corrosion inhibitor due to its non-toxic, eco-friendly properties. Silicates are inhibitors for aluminum, iron, and steel corrosion in cooling water systems. They inhibit corrosion due to the formation of protective oxides that act as barriers to oxygen diffusion to the metal surface.
Benzotriazole based corrosion inhibitor.
Benzotriazole-based compounds, such as tolyl triazole, are often used as corrosion inhibitors for Aluminum.
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What causes aluminium to corrode?
Continuing our discussion, we will scratch away the protective layer of aluminum oxide, which is initiated by either chlorides or sulfides.
Chlorides.
When chlorine, typically in a gaseous state, reacts with metal (e.g., sodium), chloride is formed. The chloride responsible for breaking the aluminum oxide layer is sodium chloride,popularly known as salt. Where do you find the salt? Of course, in an ocean.
Sulfides.
When sulfur is heated with the metal, then sulfide is formed. The two most common examples of sulfides are iron sulfide and copper sulfide. Where do you find sulfides? Of course, polluted air contains large amounts of sulfides.
Can you remove corrosion from aluminum?
Aluminium has wide applications in automobiles, aerospace, farming equipment, marine, medical, packaging, consumer goods, and industrial appliances; hence, knowing the answer to this question is essential. Yes, you can fix aluminum corrosion. However, you can only do much to prevent corrosion if the aluminum looks necessary. I will share with you some of the techniques to remove aluminum corrosion.
Use a combination of vinegar or lemon juice and water.
A combination of vinegar or lemon juice and water in equal parts is an easy way to remove normal aluminum corrosion. The proportion should be equal, meaning if you take 500 ml of lemon juice, add the same quantity of water to it. Then, dip the corroded aluminum part into the solution for a few hours overnight. Then, remove the metal part, scrub it out with a soft brush, and rinse it with clean water, wiping it with a smooth rag.
Use aluminum polish.
It is commercially available in the market. It is a non-abrasive, non-flammable, and non-toxic material. It prevents the aluminum surface from oxidation, removing dirt and dull appearance on the surface. After the application, buff the surface with a smooth rag to see the effect of aluminum polish.
Combination of baking soda and water.
Make the baking soda and water paste and apply it to the corroded area. Allow it to work for about 30-45 minutes. Then, use a soft brush to remove the paste. Rinse it with clean water.
Sanding or steel wool.
For stronger corrosion, sanding or steel wool is used. Sanding paper should be used ranging from 120 to 220 grit. Steel wool, which has been used for washing dishes for decades, can also be used to prevent the oxidation of aluminum.
Aluminum cleaners.
Commercially available aluminum cleaners are used to remove oxidation, dirt, cement, and heavy dust particles. They are mainly designed for nonferrous metals such as aluminum, stainless steel, etc., to remove stains and make them shine.
Folks, we have discussed various techniques to remove corrosion from aluminum.Some techniques use the DIY method, and others, such as polish or cleaners, use hydrofluoric acid, sulphuric acid, and phosphoric acid. Both methods are reliable and easy, but commercially available techniques require more gear. The aerospace industry, which widely uses aluminum and its alloy, can take more advantage of the above techniques than other industries.
Is aluminium anticorrosion ?
Yes, we can say aluminum is anticorrosion. It impulsively forms an aluminum oxide layer that inhibits further corrosion. It acts as an anticorrosive agent to protect from rusting. Aluminum is highly reactive and readily reacts with oxygen in the air, forming a thin layer of aluminum oxide (Al2O3), which prevents corrosion. Aluminum corrode quickly in the presence of moisture, saltwater, acidic or alkaline solutions. In abridged form, aluminum can be a corrosion inhibitor up to certain conditions. But if those conditions are not fulfilled, then it starts rusting.
But thanks to effective aluminum surface treatments, protective methods that ensure aluminum’s maximum protection ensure long-term durability and performance.
Corrosion inhibitor manufacturer in India (Indian Companies).
In India, some large-scale and medium-scale industries manufacture corrosion inhibitors.
Universal.
Universal is a prominent corrosion inhibitor manufacturer and supplier in Delhi, India. They manufacture corrosion inhibitors for oil patches, which corrode harshly. Universal provides both inorganic and organic type inhibitors. When their products are applied to oil or gas (spilling area), the rate of corrosion slows down, which depends on the surface on which the application is done. They have corrosion inhibitor products like Unicor 35 gas pipeline, INIHIB (packer fluid), Unicor 101, Unicor 102, Unicor 103, Unicor 104, Unicor 105, Unicor 106, Unicor 107, Unicor 108, etc.
Acura Organic Limited.
Acura is a renowned specialty chemical company that has been providing various chemicals for 40 years. The company has around 27 products that are used for different applications. One of the products is a corrosion inhibitor product. The corrosion inhibitors such as HCL acid, HF acid, sulphamic acid, citric acid, phosphoric acid, nitric acid, propylene glycol, mono ethylene glycol, diethylene glycol, brine, concrete, copper, etc., are sold by the company either globally or domestically.
Imperial Oilfield Chemicals Ltd (ICPL).
It is one of the major corrosion inhibitor manufacturers in India and is top-ranked in Gujarat. Corrosion inhibitors such as Hydrotesting corrosion inhibitors, Oil line corrosion inhibitors, Coke unit corrosion inhibitors, Water soluble corrosion inhibitors, Acid corrosion inhibitors, Gas line corrosion inhibitor are their primary products.
Maxwell Additives.
Maxwell Additives Pvt Ltd, Vadodara, India, was founded in 1988. It manufactures and exports various specialty chemicals, polymers, corrosion inhibitors, etc.
Jay Dinesh Chemicals.
The company has been a manufacturer, supplier, and manufacturer of corrosion inhibitors since 1981. The product is an oil field corrosion inhibitor used for corrosion caused by gas.
Ashahi Chemical Industries.
The company produces corrosion inhibitors for the oil and gas industries. Whenever pipelines need to be protected, Asahi Chemicals provides various effective corrosion inhibitor product
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