During the manufacturing and processing periods for various steel, copper and other metal formats, it’s possible various surface contaminants may be present. From mill scale to several other potential such contaminants, these may be acceptable for the metal – or in other cases they may not be, and the metal may require a clean, pure surface for a given application. In this case, a process called pickling and oiling will often be used.

At Wasatch Steel, we’re happy to detail the properties of any of our steel products, plus provide several steel services to alter certain properties and meet your precise needs. In this two-part blog series, we’ll go over everything you need to know about both parts of this process, why they’re commonly performed and some of the metal types and industries that rely most on the pickling and oiling process.

Pickling Basics

The first part of this process is known as pickling, which is a metal surface cleaning process. Pickling is mostly done after a given metal has already been formed, allowing its surface to come into contact with an acid that helps clean it.

This acid, known as the pickling liquor, will vary based on the precise metal being used. In the majority of cases for low-alloy steel, this liquor will be hydrochloric acid. In other cases, metals may be resistant to certain acids, and a more powerful one will be used – or even a rarer two-step method for particularly resistant metals.

How Pickling is Done

The steps of the pickling process generally go as follows:

• The metal will be rinsed with a solution that removes large dirt or debris particles, preparing it for pickling.
• The metal is placed into a pickling liquor bath and fully immersed, at which point the acid that makes up this bath begins to remove impurities from the metal surface.
• When a specific time limit is reached, the metal is removed to prevent acid overexposure.
• The metal is rinsed again, then typically passed through the oiling process from here.

Oiling Process

Ideally, the pickling process will leave a metal with no surface discontinuities while experiencing limited metal loss. Immediately after this process, oiling will generally be done.

Oiling is put in place to protect a given metal that’s been pickled from major corrosion once it’s exposed to the atmosphere. Steels, for instance, will commonly see flash rusting after the pickling process – but if they are oiled, this will not be a concern. Oiling involves applying a specific oil to the surface of a recently pickled and rinsed metal, oil that prevents corrosion and allows the metal to be stored long-term with minimal oxidation. Later on, if a fabrication process requires the removal of this oil, this is easily possible.

For more on the pickling and oiling process for steel and other metals, or to learn about any of our steel products or steel services, speak to the staff at Wasatch Steel today.