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Stainless Steel chemical Passivation Factors You Need To Know

chemical passivation

Industrial manufacturing companies need stainless steel because it is one of the most appropriate metals that industries can use since it cannot easily corrode. However, as everything becomes contaminated, then stainless steel also gets affected by impurities, just like any other thing. This is how these industries use chemical passivation for layering with oxide to protect the stainless steel surface and also to guarantee its longevity. Some of the biggest industries, like aerospace, chemicals, FMCG, pharmaceuticals, and more, are using chemical passivation processes for the removal of contaminants and to assure the durability of their stainless steel systems.
Before moving ahead, let us understand how ancient people were protecting metals and the further evolution of picking machines. Initially, humans were using oil, paint, and iron coating to protect metals from rusting and other contaminants. However, these ways of protecting metals were not sufficient; till the 19th and 20th centuries, we got to know the importance of pickling and passivation of chemicals and started its application over metals. This way, the modern chemical pickling and passivation solution came into existence. 

Passivation of Stainless Steel:

Chromium forms an oxide layer over stainless steel, which protects it from rusting and corrosion. However, despite its ability to boast of natural corrosion resistance powers, The role of chemical passivation emerges here to protect the metal. Whether the impurities are iron particles or of any other type, passivation solution can protect metals effectively. It does not only cleanse the stainless steel but also increases the corrosion resistance power that stainless steels provide. 

Understanding passivated stainless steels

To understand this topic further, you need to know about the passivated stainless steels. Let us understand it more. 

Passivated stainless steel

Passivated stainless steel is already chemicalized to form an oxide layer that could protect stainless steel from corrosion. 

What is a Passivated Finish?

The final appearance of stainless steel after running a chemical passivation process is known as a passivated finish. However, the appearance of stainless steel does not get affected in this process. 

The History of Passivation

The understanding regarding chemical passivation came into existence during the 19th and 20th centuries. However, discoveries in chemistry and metallurgy impacted this process significantly. 

Early Developments in Metal Treatment

Oil, tar, and paints are the earliest materials used in metals to protect them from corrosion and rusting; however, these were not so effective. With the passage of time, scientists used acid as a chemical passivation material to clean the metals, and they got amazing results from this test. This way, the use of pickling and passivation through chemicals started in industries. Since 2000, most industries started using pickling of stainless steel to protect from impurities. 

Key Advancements in the Passivation Process

In 1913, Brearley developed stainless steel that greatly affected the metal industry. This way, the passivation process became popularized. Acids like nitric and sulfuric are used to remove impurities from stainless steel. As stainless steel itself has corrosion resistance, however, if it gets impure due to the application of welding in stainless steels, Since the welding cleaning machine came into existence, the use of chemical passivation has become easier than ever. 

Different Types of Passivation for Stainless Steel

There are various ways used in the passivation process of steels. Have a glance at them before choosing a pickling and passivation process. 

Citric acid passivation

Citric acid passivation is one of the most effective passivation chemicals used in stainless steel to remove impurities. Citric acid is most preferred by FMCG companies due to its nontoxic properties. Let us know about the advantages and disadvantages of citric acid when used for stainless steel passivation. Have a glance at the table stated below. 

Citric acid passivation

Advantages

Disadvantages

Eco Friendly

It is mild in harming the environment.

Not aggressive as nitric acid

Non toxic

Safe for FMCG and Pharmaceuticals

It can require longer treatment times.

Cost effective

Cheaper as compared to nitric acid

nil

Nitric Acid Passivation

Nitric acid is normally used in removing impurities from metals. For instance, since it is highly efficient in the removal of impurities from stainless steels, aerospace industries use nitric acid to remove contaminants on the surface of stainless steel.

Electrochemical Passivation

When electric current is used to apply chemical solution over stainless steel is known as electrochemical passivation. This process is effective in complex structures of stainless steel where manual application of chemicals is not possible. 

Why passivate stainless steel?

Durability and resistance to rusting are the primary goals to passivate the stainless steels. There are various types of contaminants present in stainless steel surfaces that require a cleansing process to remove these particles. It not only prevents rust but also enhances the durability of metals for a long period of time. 

How Passivation Works

Citric and nitric acid are used to remove contaminants from stainless steel surfaces. Let us understand the chemical reaction behind this process. 

The Chemical Reaction Behind Passivation

Passivation is a controlled chemical reaction process used in the stainless steel surface and passivation solution, preferable nitric or citric acids. Due to this process, chromium in stainless steel develops an oxide layer that helps protect stainless steels from corrosion. 

How the Oxide Layer Protects Stainless Steel

The oxide layer formed during passivation of chemicals can itself repair, if damaged, the long-term corrosion resistance. This invisible layer is crucial to protecting stainless steel from impurities and corrosion. 

When Should Stainless Steel Be Passivated?

Passivation of stainless steel is very essential so that machines can work efficiently and also for quality products. Let’s learn why the passing of stainless steel is important.

After welding

When stainless steel goes through the welding process, it gets affected by the passivation of chemicals such as nitric or citric acid. With the chemical research and development, now we have effective chemicals such as K2 pickling paste that optimizes the longevity of stainless steels.

Machining process

The machining process often leaves various iron residues in the stainless steels that require effective passivation chemicals to remove these impurities. 

When to passivate stainless steels

Example application

After welding

Construction and pipelines

After machining

Aerospace components

In corrosive environments

Marine and chemical plants

Conclusion

Are you looking for chemical passivation of your stainless steel surfaces? In order to protect stainless steel machines and surfaces from corrosion and impurities, one cannot skip the application of effective pickling chemicals. In addition, the welding process of stainless steel also affects the longevity of metals. So, the application of effective surface treatment chemicals ensures the quality, productivity, and longevity of your machines.