Stainless steel can corrode in service if there is contamination of the surface. Both pickling and passivation are chemical treatments applied to the surface of stainless steel to remove surface contaminants that occur due to corrosion and assist the formation of a continuous chromium-oxide, passive film.
At Control Electropolishing, we offer a full line of pickling and passivation services, with either nitric or citric acid, depending upon the part and your needs. Our line has two independent cleaning tanks used to prepare your parts prior to processing.
Chemical Treatment Options
Stainless steel can corrode in service if there is contamination of the surface. Both pickling and passivation are chemical treatments applied to the surface of stainless steel to remove surface contaminants that occur due to corrosion and assist the formation of a continuous chromium-oxide, passive film.
Pickling and passivation are both acid treatments and neither will remove grease or oil. If the fabricated part is dirty, it may be necessary to use a detergent or alkaline cleaner before the pickling or passivation process can begin. At Control Electropolishing, we offer a full line of pickling and passivation services, with either nitric or citric acid, depending upon the part and your needs. Our line has two independent cleaning tanks used to prepare your parts prior to processing.
Pickling
Pickling is the removal of any high temperature scales and any adjacent low chromium layers of metal from the surface of stainless steel by chemical means.
Consider the following as an example of good post-weld practice: first, the steel has been heated by welding, heat treatments, or other means to the point where the surface has changed color. A chromium depleted layer forms on the surface of the steel underneath the oxide layer—the lower chromium content causes less corrosion resistance. To restore the metal to the best corrosion resistant performance, the damaged metal layer must be removed, exposing a fully alloyed stainless steel surface.
Mechanical removal may leave abrasive or other particles embedded (interfering with corrosion performance) or may be impractical, so chemical means are usually employed.
Procedures incorporating pickling solutions remove the scale and the underlying chromium depleted layer and restore the corrosion resistance while also removing contaminants such as ferrous and ferric oxide particles. After processing, parts are rinsed in a deionized water tank to accelerate the drying process and leave your parts free of stains, fingerprints, giving you a clean passive surface.