>Surface rust spots/Customers purchase a batch of 304 stainless steel plates for outdoor decoration materials. After one month of use, the rust spots appear on the surface of the stainless steel plates. The customers think that it is the cause of 304 corrosion resistance, so they raise quality objections. 304 stainless steel under normal use conditions, the occurrence of rust spots in the outdoor within 1 month is an abnormal phenomenon, so it is necessary to analyze the causes of stainless steel rust spots. Through sampling analysis and observation with an electron scanning microscope, it was found that the rust spots contained certain organic substances. After detection by X-ray spectrometer, it was found that the rust spots contained a certain amount of silicon, calcium, chlorine and trace elements of aluminum, sulfur, potassium, etc. In addition, silicon, calcium, etc. are agglomerated on the rust spots, and chlorine is distributed throughout the defect range. This indicates that the rust stain defects may be composed of a mixture of chlorine-containing organic substances and soil. And after testing, these rust spots are only attached to the surface of the steel plate, and can be removed by mild cleaning with detergent. From this, it can be determined that these rust spots are not caused by the rust of the stainless steel itself, but because of the combined action of outdoor rain and environmental pollutants. Deposited on the surface of the stainless steel plate. Thoroughly clean the stainless steel surface, the rust spots can be completely removed. It is worth noting that due to the serious environmental pollution, acid rain, dust and other substances form deposits on the surface of stainless steel. These deposits should be cleaned in time. If the time is long, it can also lead to further corrosion and rust of stainless steel.