Stainless steel is an important metal material that has gained wide application in the manufacturing industry due to its high hardness and corrosion resistance. This material should be properly pretreated before surface treatment. As the stainless steel parts in the machining and molding process, the surface is likely to exist sticking to the oil, the existence of burrs to form a rough surface and oxides and other defects, if the surface treatment before the surface treatment, there is no such oil, burrs, uneven surface and oxides removed, the subsequent surface treatment processing is difficult to obtain satisfactory results.
Pretreatment is the surface of stainless steel parts in the surface treatment process, including pickling, chemical polishing, electrochemical polishing, electroplating, passivation, with black, with color, chemical processing, and other surface treatment methods must be carried out before the important processing steps. Selection of pretreatment should give full consideration to the differences in the surface state of stainless steel parts, but also consider the quality requirements for the subsequent treatment of materials, choose the most appropriate pretreatment method.
Dirt to be removed for pretreatment
Removing dirt is an important task in the pretreatment of stainless steel parts. Stainless steel surface in the pretreatment to remove the dirt is divided into organic and inorganic two major categories.
Organic dirt is mainly a variety of oil, including mineral oil, animal oil and vegetable oil. Mineral oil in diesel fuel, oil, petroleum jelly and paraffin, etc.; animal oil is animal fat, lard, tallow and fish oil, etc.; vegetable oil is soybean oil, tea oil, rapeseed oil, etc.. These organic dirt is the main source of stainless steel parts used in the processing of lubricating oil, cutting oil, quenching oil, grinding paste and polishing paste, as well as steel parts are stained by the touch of workers fingerprints and so on.
Inorganic dirt includes soil, dust particles, oxides generated during heat treatment, etc.
Stainless steel parts pretreatment steps
The first step is the surface mechanical leveling, which is the use of mechanical grinding, polishing methods, is the steel parts to achieve a certain surface finish, thereby eliminating the roughness of the stainless steel surface; the second step is to use alkaline solutions or organic solvents to remove the oil on the surface of stainless steel parts; the third step is to use the method of pickling to remove the surface of the stainless steel parts of the oxides; the fourth step is a weak corrosion, the surface to be treated to be activated, so that the surface of the surface of the passivation. Remove the passivation film present on the surface, exposing the internal metal crystalline organization.
Stainless steel surface pretreatment methods
Mechanical method, which is the use of grinding machine, polishing machine or other mechanical grinding and polishing, eliminate the roughness of the surface of stainless steel parts.
Chemical method, this is the use of alkaline solution or organic solvent dissolution of stainless steel parts for degreasing, dissolving and removing stainless steel surface oil, as well as the use of acidic solution on the stainless steel parts for pickling, removing stainless steel pieces of the surface of the oxides of the processing process.
Electrochemical method, which is the use of electrochemical corrosion method, remove the stainless steel surface oil or passivation film processing.
Rolling, centrifugal rolling, centrifugal disk finishing and rotary finishing, these four processing methods are suitable for small parts, they have the role of leveling and removing oxide skin.
Sandblasting, when the area to be prepped is large, is a relatively efficient method of removing oil and oxidized skin.
