Discussion on Improvements for Corrosion Issues
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One of the main reasons for the heavy workload of my drivers and maintenance staff is that the equipment cannot withstand the corrosion caused by the harsh conditions at the site. Intergranular corrosion. The material for the grooves should be austenitic stainless steel; it is not known whether it is 304 or 316L (testing solutions can be purchased for this purpose). The lower carbon content helps to minimize the formation of carbides in the heat-affected zone near the welds, and the formation of carbides can lead to intergranular corrosion in stainless steel under certain conditions (where corrosive substances may remain at the bottom). Currently, the erosion phenomenon in the grooves is likely to be of this intergranular erosion type, as the areas where corrosion leakage occurs are all in the thermally deformed zones around the welds. Currently, the method used for sealing cracks is still patch welding with gussets, using A132 electrodes, but this does not prevent leaks from occurring again. Currently, we are considering using PTFE spraying for corrosion protection, but the cost might be high. Are there any other methods available? ① A. The materials that come into contact with the stainless steel tank include sulfuric acid, formic acid, soda, cadmium powder, nitrites, steam, etc.; occasionally, hydrochloric acid containing chloride ions also comes into contact with it. The operating conditions are extremely harsh.
Come on up! Why isn’t anyone responding?
If the temperature is not high, spraying PTFE is a good option. The key point is that baking is required after spraying, which may make the process inconvenient. The price isn’t very high. There are specialized companies in Beijing that sell coatings for this purpose; you can search for them online. There are also those that do not require baking, but they operate at lower temperatures.
How much is it to spray PTFE per square meter? The operating temperature is not high, below 80 degrees; I think fiberglass can handle it!
The most cost-effective method is as follows: solution treatment. For example, the welded parts are heated to 1050–1100°C and then quenched to prevent further deposition. Welding should be carried out quickly, and the weld area should be cooled rapidly to prevent the material from remaining in the sensitized zone. Solution treatment is an effective method to eliminate intergranular corrosion in stainless steel, as it can reduce the carbon content at the grain boundaries. Other options such as stabilization treatment, or the use of ultra-low carbon stainless steel or duplex steel, are also quite expensive.