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What Is Passivation: The Secret To Long-Lasting Metal Protection

by | Mar 21, 2023

Passivation is a process used to protect metal surfaces from corrosion and oxidation. It is a simple yet effective way to extend the life of metal components and ensure that they remain in optimal condition for longer. Passivation is an important part of the manufacturing process for many industries, from aerospace to medical to automotive. It is especially important for stainless steel, as it helps to keep the metal from rusting and corroding.

Passivation is a chemical process that removes free iron particles from the surface of a metal and forms a thin, protective layer of oxide. This layer of oxide helps to prevent further oxidation and corrosion, and also helps to enhance the appearance of the metal. The process of passivation is relatively simple, and it is often used in combination with other treatments such as pickling or electroplating.

Passivation is an important part of the manufacturing process for many industries, as it helps to ensure that metal components remain in optimal condition for longer. It is especially important for stainless steel, as it helps to keep the metal from rusting and corroding. Passivation is also used to enhance the appearance of metal components, as the oxide layer helps to give the metal a brighter, more uniform finish.

In this article, we will discuss what passivation is, how it works, and what materials can be passivated. We will also discuss the benefits of passivation, the passivation process, passivation versus pickling, passivation standards and specifications, and some frequently asked questions. Finally, we will provide an introduction to the process of passivation and how it can help to protect metal components and extend their lifespan.

 

What Is Passivation?

The process of passivation is used to shield metal surfaces from oxidation and corrosion. It entails applying a chemical solution to the metal’s surface in order to create a barrier that stops corrosion and oxidation. This layer of defense is referred to as a “passive layer” and is frequently called “passivation.” Many various kinds of metals, such as stainless steel, aluminum, copper, and brass, are protected by passivation.

By creating a barrier between the metal surface and the outside world, passivation works. Via this barrier, oxygen and other corrosive substances are kept away from the metal. A metal surface that is more resistant to corrosion and oxidation is the end result. The metal surface does not need to be cleaned and polished as frequently thanks to passivation, which contributes to a reduction in the time and effort needed to maintain it.

The process of passivation is reasonably easy and inexpensive. It can be carried out internally or contracted out to a reputable metal finishing business. The procedure normally entails coating the metal surface with a chemical solution, which is then let to sit for a while. As a result, the chemical can enter the metal and create the barrier. When the metal surface has been passivated, it is cleaned and polished to bring back its original sheen.

 

How Does Passivation Work?

Metals are shielded from corrosion by a process called passivation. It functions by depositing a thin layer of a shielding substance on the metal’s surface. This layer serves to stop the metal from corroding and rusting since it is often composed of a substance that is insoluble in water and other liquids.

Nitric acid or another chemical solution is frequently used during the passivation process to clean the metal’s surface of any grime, grease, or other contaminants. This helps to create a clean surface that can be more easily protected with a layer of the protective material.

The coating is put on the metal after it has been cleaned. This substance is typically a blend of substances that are insoluble in water and other liquids, such as chromates, phosphates, or nitrates. These substances help to prevent corrosion by forming a thin layer on the metal’s surface.

The passivation process also helps to improve the appearance of the metal, as the protective layer gives it a glossy finish. This also helps to make the metal more resistant to scratches, which can cause corrosion over time.

The passivation process is an effective way to protect metals from corrosion and improve their appearance. It is used on a variety of metals, including stainless steel, aluminum, copper, and brass. The process is relatively simple and cost-effective, which makes it a popular choice for many industries.

 

What Materials Can Be Passivated

A procedure called passivation can be used to shield a variety of metal surfaces, including those made of titanium, stainless steel, and other alloys. It is the best approach to increase the lifespan of metal parts and stop rust and corrosion. The process of passivation cleans the metal surface of any impurities like grease, oil, or dirt before forming a barrier film to stop further contamination.

Depending on the passivation procedure being employed, different materials can be passivated. Aluminum, titanium, and other alloys as well as stainless steel are typical materials that can be passivated. Since it is so resistant to corrosion and rusting, stainless steel is the metal that is passivated the most frequently. While titanium and aluminum can also be passivated, their method is different from that of stainless steel. To passivate other metals, certain procedures might be necessary.

In order to offer the best protection while passivating metal surfaces, it is crucial to employ the right procedure for the material. Depending on the metal, the environment in which it is used, and the level of protection sought, a particular technique will be utilized. For instance, while aluminum and titanium need a distinct procedure, stainless steel can be passivated using either a nitric acid or citric acid process. In order to make sure the right procedure is applied for the metal in issue, it is crucial to seek professional advice.

Titanium

 

Benefits Of Passivation

Passivation Removes Surface Contamination

As indicated above, one of stainless steel’s advantages is its ease of cleaning. Yet, the cleaning procedure itself may produce risks that could harm the item’s performance in the future. The passive layer can be harmed by abrasive chemical cleaners because it is only a few Angstroms (or molecular levels) thick. Moreover, it is extremely vulnerable to mechanical damage from both abrasive cleaners and the cleaning instruments themselves. The impact and movement of dry parts inside the vessel or piping itself can cause additional damage by abrading the chromium oxide and removing or weakening it.

 

Passivation Increases Corrosion Resistance

Along with cleaning up impurities, the chemical passivation process also renews and enhances the chromium oxide layer, which increases the steel’s corrosion resistance. Beyond surface iron, the alloy of stainless steel itself also poses a risk of corrosion. Metallic ions in the metal, particularly iron, will gradually move through the spaces between its crystals. Ultimately, iron can emerge in the passive layer from the bulk alloy through the middle, nickel-rich transition layer, providing fresh opportunities for iron oxide to develop. Often occurring passivation procedures eliminate the iron atoms before they may do any harm.

 

Corrosion Resistance

 

Passivation Reduces the Risk of Product Contamination

Contrary to chrome and chromium oxide, iron is a strong chemically reactive substance that can mix with water or other ingredients to form undesirable compounds that can lessen, if not entirely damage, a product’s effectiveness. Moreover, passivation bonds (chelates) with other pollutants, enabling them to be removed with the passivating solution and flushed out of the system together with any free iron that may still be present.

 

Passivation Allows Extended System Maintenance Intervals

By renewing the chemically passive layer through a regular schedule of passivation treatment, the need for a total system shut down to clean and restore the stainless steel components is reduced, thus increasing the time between such intervals. As a result, it is crucial to start routine passivation treatments before commissioning a new vessel or system since passivation will clear away any debris from the building process.

 

Passivation Saves Money and Reduces Downtime

Regular passivation helps lower the possibility of unplanned system shutdowns in addition to lengthening the intervals between the necessary but expensive planned system maintenance intervals. Passivation lowers the chance of contamination from the system itself while also lowering the possibility that such contamination will result in the loss of an entire production lot. The unanticipated cost of putting the system offline in terms of rescheduling and other logistical concerns is frequently equal to the expenses in lost material. The “extra” cost of routine passivation becomes a worthwhile investment when you factor in the cost of identifying and removing the contamination source, as well as the associated cleaning before reactivating the system.

 

The Passivation Process

The passivation process is a critical step in providing long-term protection for metal parts and components. In order to create a protective oxide layer on the surface of stainless steel, loose iron particles must be removed chemically through a process called passivation. This covering aids in shielding the metal from rust and other types of harm.

Nitric or citric acid solutions are frequently used in the passivation process and are applied to the metal’s surface. A clean and smooth surface is left behind after the acid helps to eliminate any loose iron particles and other contaminants from the surface. After the surface has been thoroughly cleaned, a shielding oxide layer forms, acting as a deterrent to corrosion and other types of harm.

The process of passivation can be carried out manually or with the aid of automated equipment. During manual passivation, the acid solution is applied to the metal’s surface using a brush or cloth. A machine that applies a precise amount of acid solution to the surface is used in automated passivation. This method is more effective and works well for passivating many pieces at once.

It’s important to use the right kind of acid solution and to adhere to the manufacturer’s recommendations when passivating stainless steel. The surface should be evenly coated with the acid solution, which should then sit for a while before being rinsed off. By doing so, the proper formation of the oxide layer and suitable protection of the metal are guaranteed.

The passivation procedure is an important step in offering metal parts and components long-term protection. A protective oxide layer is created by eliminating free iron ions and other contaminants from the surface, assisting in preventing corrosion and other types of damage. When passivating stainless steel, it’s crucial to adhere to the manufacturer’s recommendations and use the right kind of acid solution. By doing so, the proper formation of the oxide layer and suitable protection of the metal are guaranteed.

 

Passivation Vs Pickling

Passivation and pickling are two processes that are used to protect metal surfaces from corrosion. While using chemicals to clean and preserve metal surfaces is a part of both processes, there are some significant distinctions between them.

Metal surfaces can have their corrosion resistance increased through the chemical process of passivation. To get rid of any pollutants or impurities that might be on the metal’s surface, an acid or chemical solution is used. The procedure also contributes to the development of a corrosion-resistant oxide layer on the metal surface.

Pickling, on the other hand, is a chemical process that is used to remove rust and other contaminants from metal surfaces. To get rid of any rust or pollutants that might be on the metal’s surface, an acid or chemical solution is used. The procedure also helps to give the metal surface a smooth finish that helps to prevent corrosion.

The fundamental distinction between pickling and passivation is that pickling is used to clean rust and other impurities from metal surfaces, whereas passivation is intended to strengthen the corrosion resistance of metal surfaces. Pickling is used to give the metal surface a smooth finish, whereas passivation is used to add a protective oxide coating to the metal surface.

In conclusion, passivation and pickling are two processes that are used to protect metal surfaces from corrosion. Pickling is used to get rid of rust and other pollutants from metal surfaces, while passivation is used to make metal surfaces more corrosion resistant. Although both procedures use chemicals to clean and shield metal surfaces, there are some significant distinctions between them.

 

Passivation Standards And Specifications

Understanding the rules and requirements that govern passivation is crucial since it is an important stage in the metal finishing process. Organizations like ASTM International (previously known as the American Society for Testing and Materials) set passivation standards, which help guarantee that the passivation process is carried out correctly and safely.

These guidelines and requirements aid in ensuring that the passivation procedure is carried out appropriately and securely. Manufacturers may make sure their products are secure and of the greatest caliber by adhering to the guidelines and requirements established by groups like ASTM International.

 

ASTM A967

The ASTM A967 is the standard for chemical passivation treatments for stainless steel parts. This standard specifies the conditions for the chemical passivation procedure, including the permitted chemical types, their concentrations, the solution temperature, and the passivation period. The ASTM A967 also outlines the testing that must be done to ensure that the passivation process has been completed correctly.

 

ASTM A380

The ASTM A380 is the standard for cleaning and passivation of stainless steel parts. This standard outlines the requirements for the cleaning and passivation process, including the types of cleaning chemicals that can be used, the concentration of the chemicals, the temperature of the solution, and the duration of the cleaning and passivation process. The ASTM A380 also outlines the testing that must be done to ensure that the cleaning and passivation process has been completed correctly.

 

ASTM A959

The ASTM A959 is the standard for the chemical passivation treatments of stainless steel parts that are used in the aerospace industry. This standard specifies the conditions for the chemical passivation procedure, including the permitted chemical types, their concentrations, the solution temperature, and the passivation period. The testing that must be carried out to confirm that the passivation procedure has been carried out appropriately is also described in the ASTM A959.

 

ASTM B912

The ASTM B912 is the standard for the chemical passivation treatments of stainless steel parts that are used in the medical industry. This standard outlines the requirements for the chemical passivation process, including the types of chemicals that can be used, the concentration of the chemicals, the temperature of the solution, and the duration of the passivation process. The ASTM B912 also outlines the testing that must be done to ensure that the passivation process has been completed correctly.

 

Final Thoughts

Passivation is a crucial procedure that keeps stainless steel from corroding and keeps it looking brand new. Therefore, it is unquestionably an effective way to increase productivity and service quality.

Even though the procedure is straightforward, common passivation can be completed at home with a basic kit. You must work with a reputable business if you want production-grade stainless steel passivated parts. This is because of the importance of the performance steel in service.

Moreover, you can save a lot of money in maintenance when steel is properly passivated to prevent failure in service. Reach out to us today to about your passivation needs or learn more about our passivation process.

Ƶƽ is a full-service surface finishing company specializing in the commercial aerospace, defense, space and satellite industries. With ten strategically located sites across the United States, Valence provides a start to finish solution from NDT and chemical processing (including steel passivation), to paint and sub-assembly.

 

FAQs

Does Passivation Remove Rust?

Passivation does not remove rust from metal surfaces. Its purpose is to shield the metal from oxidation and further corrosion. Before the passivation procedure starts, any rust that is present should be eliminated.

 

How Can You Tell If Steel Is Passivated?

Steel that has been passivated will generally have a bright, shiny finish. It will also be resistant to corrosion and oxidation. If the metal has a dull, matte finish, it has not been passivated.

 

What Happens If Stainless Steel Is Not Passivated?

If stainless steel is not passivated, it will be more susceptible to corrosion, oxidation, and staining. It may also be more prone to developing rust spots and other signs of wear and tear.

 

Can You Passivate For Too Long?

It is possible to passivate for too long, which can result in the metal becoming brittle and cracking. Passivation should be done for the recommended amount of time to ensure that the metal is properly protected.

 

Does 316 Steel Need To Be Passivated?

Yes, 316 steel should be passivated to protect it from corrosion and oxidation. Passivation will help to keep the metal looking its best and prevent it from becoming damaged over time.

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