The post-process cleaning requirements of bipolar stainless steel are no different from those of other stainless steels. Post-process cleaning is important as the temperature between the control layers or the use of protective gases during welding. Stainless steel, which has not been properly cleaned after processing, can fail at temperatures much lower than the master or in environments that are much less corrosive. This means that unless the processed material maintains or restores the best surface, the additional costs of using materials with better corrosion resistance are wasted. Welding splashes, welding oxidation colors, marker pen marks, arcing points, and bite edges can all become gaps in a watery environment. At the same time, they may have corrosive potentials that differ from stainless steel surfaces, so electrochemical reactions may occur. It is important to eliminate these defects, which have a destructive effect on the protective passivation membrane.

1, mark pen prints, paint, dust and oil

All of these surface contaminants can be the source of crevices and stainless steel pitting or crevice corrosion. In addition, they can lead to carbon pollution. Carbide procuring may occur if the next welding is performed. The material becomes sensitive and produces intercrystalline corrosion during use. Solvents are applied to remove these contaminants.

2, embedded iron (containing iron compound pollution)

Embedded or free iron on stainless steel is caused by the processing or transportation of stainless steel with carbon steel tools. If stainless steel is treated with a carbon steel tool or processed near where it is stored, the iron is transferred to the stainless steel surface. Iron then rusts in a humid or humid environment and can cause corrosion on stainless steel surfaces. One solution is to avoid all contact between stainless steel and carbon steel. Stainless steel should be processed using only stainless steel tools, stainless steel wire brushes, stainless steel fixtures and new, unstained grinding wheels. Tools are often numbered in different colors in the workshop.

However, it may be unrealistic and uneconomical to avoid carbon steel tools at all and to avoid iron pollution in the workshop environment. Another option is to acknowledge the possibility of iron contamination, but promise to ensure that stainless steel is removed before it is put into service. Methods for removing iron contamination include mechanical cleaning, chemical cleaning, or a combination of mechanical and chemical cleanup. The optimal cleaning method depends on the size and shape of the equipment, the expected service environment and some practical issues, including the disposal of the waste. A common cleaning method is chemical treatment with nitric acid, which dissolves free iron on stainless steel surfaces but does not erode stainless steel or passivated film protective layers. Many different chemical cleaning methods can achieve the desired results. The ASTM A380 (standard method for cleaning, rust removal and passivation of stainless steel components, equipment and systems) explores the details of the cleaning method in detail. Users should be familiar with the security issues listed in ASTM A380.

ASTM A 967 (the standard specification for chemical passivation treatment of stainless steel components, in place of the U.S. federal standard QQP-35c) provides information on the selection of appropriate test methods to demonstrate that stainless steel has been effectively passivated. The standard wants buyers to specify the passivation level required, allowing manufacturers to use cost-effective and applicable methods for surface treatment.

3, welding splash, welding discoloration, solder, slag, arc spots

All of these defects can occur during welding. They can form gaps and induce crevice corrosion in chloride-containing environments, and these defects should be avoided or removed after welding. The use of splash-proof compounds during processing prevents welding splashes. Welding discoloration reduces corrosion resistance due to the destruction of the passivation layer. Cleaning the back of the weld with inert gas protection and inert gas prevents severe weld discoloration or reflux. However, usually the reflux color cannot be completely avoided and must be removed in the post-weld cleaning. Solder and solder residue inclusions and arc spots should also be removed before the equipment is put into service. Welding splashes, weld oxidation colors, solder, solder slag, arc spots and welding bite edges can all be removed using mechanical cleaning methods such as fine abrasive grinding. Fine grinding wheels should be used, as rough grinding marks during use can cause sediment to adhere and create gaps that cause corrosion at the crevices.

A notable feature of bipolar stainless steel is that the welds are thin, sticky and chemically resistant to chemical cleaning than Australi stainless steels, which are resistant to corrosion. The color change of the weld can be chemically cleaned by acid washing method, for example, with 20% nitric acid-5% hydrofluoric acid solution to acid wash 2205. The solution dissolves chromium oxide and erodes stainless steel, removing the chromium-poor layer. Acid wash paste has a similar effect, but is easier to handle large workpieces and can be used as a substitute for acid solutions. However, it should be recognized that acid wash paste during flushing produces a harmful solution and that it is the user’s responsibility to take appropriate safety, operation and treatment measures. Depending on the corrosion resistance of bipolar stainless steel, less aggressive or stronger acids can be required to remove oxidation. Studies have shown that chemical cleaning after welding provides optimal corrosion resistance. Learn moreBipolar stainless steel information: http://www.xhcs.com/news/