The material of the fire truck tank is generally carbon steel, but in order to prolong the service life of the fire truck tank, we will choose stainless steel as the material of the tank body, but after using it for a period of time, the customer service staff reported that the water tank was rusty and leaking. We conducted a return visit, investigation, and analysis for this situation, and finally came to the conclusion that the interior of the stainless steel water tank of the fire truck must be anti-corrosive. After entering the water tank for inspection, it was found that most of the corrosion occurred in the weld, the area near the weld and the intermittent weld, and the corrosion products accumulated. According to the analysis of the corrosion morphology, the cause of the stainless steel material, processing state and use environment was analyzed.
After investigation, the method used for water tank welding is gas shielded welding, 308 stainless steel wire, but the anti-sloshing plate inside the water tank is intermittently welded, and the gap is not treated, and the splashes and scales near the internal bead are not treated. . We all know that when the gap is between 0.025-0.1mm , the sensitivity of crevice corrosion will be greatly increased, and welding spatter may destroy the passive state of the stainless steel surface, leaving the stainless steel in a partially activated state and becoming weak in pitting corrosion. Not only that, in the process of blanking, bending, transferring, etc., it is inevitable that the stainless steel surface will be damaged to a certain extent, and the stainless steel will be contaminated by iron ions and cause pitting.
It was learned through communication with the fire brigade that tap water is generally stored in water tanks of fire trucks, and river water and lake water are often replenished in the vicinity of fire sites. Entering the inside of the rusted water tank, you can see that a large amount of dirt is deposited on the bottom of the water tank, and there is a thin layer of water-alkali stain on the inner wall of the tank.
We all know that it is an important ion that causes corrosion of stainless steel. Generally, tap water is sterilized with chloroform. There is an inevitable entrainment of Cl- in tap water, and there are more impurity ions in river water and lake water. Filling into stainless steel water tanks provides an environmental basis for corrosion of stainless steel.
In summary, during the processing and use of stainless steel water tanks, there are indeed conditions that meet its corrosion, so it is necessary to carry out anti-corrosion treatment on the interior of stainless steel water tanks.
At present, there are many methods for waterproofing and anticorrosion, such as plastic, glass fiber reinforced plastic lining, polyurea coating, paint coating, etc. From the consideration of cost and construction convenience, it is recommended to use paint coating for corrosion protection.
The water stored in the fire water tank can not only be used for fire extinguishing, but also possible to carry drinking water during disaster relief and other situations. Therefore, the coating used for internal corrosion protection should be non-toxic. After investigation, the H52-33 epoxy anticorrosive paint film is tough. , Salt, alkali, water resistance, has good resistance to salt spray and damp heat, can be used for industrial steel equipment and pipelines, drinking water systems, water treatment system protection, in line with the requirements of fire protection water tank internal corrosion.
Welding gap treatment
Intermittent welding gaps can be filled with water-resistant sealants or changed to continuous full-welding. However, considering the use of sealants for plugging treatment, the water resistance and adhesion of the sealants need to be tested. And coating and filling the gaps need to enter the water tank twice, and the workload is large. Therefore, it is recommended to change the intermittent welding to continuous welding.
Cleaning inside the jug
After the water tank is welded, it is necessary to enter the tank body to clean up the welding knobs, slag, splashes, oxide scale, etc. generated by the welding to create a good construction foundation for coating anticorrosion.
Although stainless steel has good corrosion resistance, it does not cause corrosion. It is very normal for stainless steel to cause corrosion under certain conditions, and once corrosion occurs, it is often very fast and easy to perforate. Stainless steel tank is one of the most important parts in fire fighting vehicles. Once the leakage occurs, it will affect the use of the vehicle and seriously damage the company's image. Therefore, we should get rid of the "stainless" misunderstanding of stainless steel, combine it with the actual situation, use it reasonably and deal with it in order to avoid similar quality accidents.