What Does Picture Window Mean In Construction?
What Does Picture Window Mean In Construction?
Pickling is a metal surface treatment technique used to clean metal surfaces and remove impurities, such as stains, rust, and scale. A solution called pickle liquor containing acid is used to achieve this. The process is widely used in steelmaking to descale steel.
To achieve the desired coloration and grain transfer, field samples are often used. Pickling is commonly used in family rooms, large commercial spaces that need to be light and airy, and the process is inexpensive and easy to apply.
There are other painting techniques and products that can create a similar look to pickling and are readily available at big box stores.
Pickling Process
Metal surfaces can sometimes have impurities that can impact their usage or further processing, such as plating or painting. To remove these impurities, various chemical solutions are employed, with strong acids like hydrochloric and sulfuric acid being the most common.
However, different applications can utilize different acids. Alkaline solutions can also be used to clean metal surfaces, and these solutions often contain additional ingredients, like wetting agents and corrosion inhibitors.
The process of cleaning the metal surface with an acid solution is referred to as pickling, and it is sometimes referred to as acid cleaning if no descaling is necessary.
Pickling is necessary for removing the discolored oxide layer or scale that forms on the surface of metal products during hot working processes and high-temperature processes.
The work piece is dipped into a vat of pickling liquor to remove the scale. Prior to cold rolling, hot-rolled steel is typically sent through a pickling line to eliminate the scale from the surface.
Hydrochloric acid is the primary acid used in steelmaking, although sulfuric acid was previously more commonly used. Hydrochloric acid is more expensive, but it pickles faster while minimizing the loss of base metal. This speed is required for integration into automatic steel mills that run at high speeds.
Carbon steels with an alloy content of 6% or less are typically pickled with hydrochloric or sulfuric acid, while steels with an alloy content greater than 6% require two-step pickling and use other acids like phosphoric, nitric, and hydrofluoric acid.
Rust and acid-resistant chromium-nickel steels are typically pickled in a bath of hydrofluoric and nitric acid. Most copper alloys are pickled in dilute sulfuric acid, while brass is pickled in a mixture of concentrated sulfuric and nitric acid, sodium chloride, and soot.
In jewelry making, pickling is used to remove the copper oxide layer that forms during the heating of copper and sterling silver during soldering and annealing. A diluted sulfuric acid pickling bath is traditional, but it can be replaced with citric acid.
Sheet steel that undergoes acid pickling will oxidize, or rust, when exposed to atmospheric conditions with moderate humidity. To prevent this, a thin film of oil or a similar waterproof coating is applied to create a barrier against moisture in the air. This oil film must later be removed for many fabrication, plating, or painting processes.
Disadvantages Of Pickling
Pickling has numerous disadvantages, including its corrosive nature, hydrogen embrittlement issues for certain alloys and high-carbon steels and the need to precisely control acid concentrations and solution temperatures in order to ensure desired pickling rates.
Acid cleaning is difficult to handle and not applicable to all steels, while the hydrogen from the acid can react with the surface of some metals making them brittle and prone to cracking.
All of these factors make careful consideration necessary when choosing a pickling process.
