What Is The Difference Between Pickling And Oiling?

The mill processing causes the metals to get contaminated. Sometimes these metal products are used as they are with contaminants but few applications require a clean and pure surface. If the specifications of the application mention the need for a high degree of cleanliness, there arises a need to use the process of pickling and oiling.

In the following passages, we will discuss both these processes in detail one by one. 

Pickling

It is a process that is used for surface cleaning after the metal is formed. An acid name pickling liquor is used to clean the surface of the metal. Usually, steels that have lower alloy hydrochloric acid is used. If the metals are highly resistant to acids, either a stronger acid or a pickling process involving two steps is used in order to achieve the best results. 

Process of Pickling

Firstly, the metal is rinsed properly to get rid of any dust particles or dirt. The next step is to bathe the metal in pickling liquor. When the metals in dipped in the pickling liquor, it starts working and removes all impurities from the surface of the metal. There is a certain time limit for it remains in the pickling liquor and when that time limit is reached it is removed from the acid. After taking it out it is rinsed again to secure it from the acid and then it goes to the second process known as oiling.

Oiling

This process is used to prevent oxidation. This process takes place right after the process of pickling and rinsing has been performed. This process is imperative because the metal substrates after pickling if it is exposed to the environment. If it is not performed in due time that metals get corroded rapidly. It has been observed that metal starts rusting after it has undergone the process of pickling.

Process of Oiling

This process involves the oiling of the metal after it is being pickled and rinsed in order to save it from corrosion and allows minimum oxidation for a longer duration of time. If the metal is required for fabrication, there may be a requirement to remove the oil from its surface but it should be avoided until the metal can be fabricated.

Benefits of Pickling and Oiling

• It removes contaminants, oil, dust particles, residues, and dirt.
• It is important for the fabrication process.
• It makes the metal corrosion-resistant.
• It improves the workability and machinability of the metal.

Types of Metals that can be Pickled and Oiled

Steel alloys are usually pickled and oiled.  Mostly hot rolled steel requires pickling because of the mill scale. Due to pickling, steel starts corroding rapidly and oiling becomes necessary in order to protect the steel from corrosion and rusting.  Carbon steel is also pickled but it requires strong acids because it has a higher quantity of alloying elements. Stainless steel and aluminum are also pickled for use in certain applications. Metals including brass, bronze, copper, and copper alloys are often pickled and oiled. Pickling protects the copper from oxidizing and forming a green layer.