Why does the stainless steel thermos cup rust? two

Does 304 stainless steel definitely won’t rust? No. One time, we took a customer to visit the workshop. The customer found that some stainless steel inner liner in the scrap area was rusty. The customer was puzzled. In addition, we have always emphasized to customers that when we produce stainless steel linings, the inside and outside are made of 304 stainless steel, so the customers’ eyes were full of doubts at that time. In order to eliminate the customers’ doubts, we specially invited a supervisor in the workshop who has been producing stainless steel water cups for more than 10 years to talk to the customers. explain.

The specific reason is that 304 stainless steel needs to be welded when producing the liner of the water cup. The high power of the welding and the inaccurate welding position will cause the welding position to be damaged by high temperature, and the damaged position will oxidize if it comes into contact with moisture in the air for a long time. In order to eliminate the customer’s concerns about rust, our production supervisor took the initiative to provide the customer with two identical inner pots. One was poorly welded and the other was qualified. Please ask the other party to take it back and store it in a humid environment for 10-15 days. After further observation, it was not that we artificially replaced the material. The final result was exactly what the production supervisor said. The customer cleared his doubts and cooperated with us.

316 stainless steel will also have the same problems due to the above reasons, but in addition to these reasons, another reason is that when using stainless steel water cups produced by 304 stainless steel and 316 stainless steel, do not come into contact with liquids with high salinity concentration and high acid concentration. There are standards for salt spray testing and acid testing on 304 stainless steel and 316 stainless steel. However, after these standards are published, it is difficult for people to do experiments in daily life. So you can simply understand that once the salt concentration is high and High acid concentration will destroy the protective layer on the surface of stainless steel, causing 304 stainless steel to oxidize and rust like 316 stainless steel.

When you see this, friends, when you buy a stainless steel water cup, either in the instruction manual of the water cup or on the packaging box of the water cup, many manufacturers will clearly indicate that the water cup cannot hold highly corrosive liquids such as carbonated drinks and salt water.