pickling and passivation

EPSCO’s Pickling and Passivation Services

Pickling is the process of removing a thin layer from the surface of stainless steel material using an acid chemical solution, typically a mixture of nitric and hydrofluoric acids. Stainless steel surface comes in contact with certain gases in the atmosphere when it is heated like in welding. This results in chemical reactions that cause the formation of an oxide layer or oxide scales on the surface of the stainless steel material.
While a thin layer of oxide is a protective coating that helps prevent further oxidation of stainless steel, a thick oxide layer impairs the corrosion resistance of the stainless steel material leading to potential corrosion. Pickling removes all the impurities from the surface of the stainless steel material, restores the thermally altered surface area, gives a clean good looking surface, and prepares the surface for passivation, when followed with passivation creates a thin layer of protective coating on the surface of stainless steel material.

Pickling and Passivation of Stainless Steel

This chemical treatment calls for a great deal of caution and safety. EPSCO, for more than 25 years in the region, has handled the risks and complexities involved in providing Pickling and Passivation services.
Pickling is applied using a spray brush or via immersing the metal. It might result in a relatively small material loss, typically five to ten microns. EPSCO also handles odd-shaped objects. EPSCO’s team of qualified, well-experienced chemical engineers, mechanical engineers, safety managers, and technicians work together throughout the project. The team collaborates in selecting the pickling method, risk assessment, selection of processes, execution, monitoring, and controlling of the pickling process.
With our knowledge, skill, and experience, EPSCO can complete all the pickling jobs satisfactorily, achieving the final agreed surface finish. EPSCO has carried out several pickling and passivation jobs of materials intended for the harshest environments. EPSCO personnel are very competent in all aspects of the pickling and passivation jobs and can take up any complex pickling jobs of any size.
EPSCO carries out a complete range of services including, pre-cleaning the surface of oil, grease, soil, spatter or weld flux to post-cleaning after the pickling treatment. The composition of the pickling paste depends on the level of the contamination. Pickling paste or the chemical composition is applied evenly on the surface. The ideal temperature throughout the treatment is approximately between 10 to 40 degrees celsius.
Passivation is the chemical treatment process of rebuilding a passive layer or passive film. After the pickling chemical treatment, the metal is treated with a thin passive layer of passivation gel. A passive surface film is composed of chromium-nickel oxide. The metal is treated with citric acid to remove the free iron from the metal surface.
Once the stainless steel is exposed to air, the chromium-nickel oxides react with the oxygen to form an oxide layer protecting the rest of the steel from corrosion. EPSCO uses the in-house passivation tanks to coat them with the resistant chemical.
Though stainless steel is naturally corrosion-resistant, it can still oxidize due to the inherent properties of the metal. Therefore, passivation treatment is recommended to maximize the life of metal and corrosion resistance.

Industries Served

Oil Refineries
Marine
Petrochemical Complexes
Steel Plants
Hotels
Offshore Oil Rigs
Power Stations
Air-Conditioning Companies
Engineering, Procurement & Construction Companies

EPSCO SERVICES