Corrosion issues of composite panels

The corrosion problem of composite panels depends on various factors, including the type of material, the properties of the medium, temperature, pressure, etc. In the situation you described, the face layer of the composite panel is 304 stainless steel, while the base layer is Q345R carbon steel. 304 stainless steel has better corrosion resistance compared to Q345R carbon steel, especially in oxidizing media such as nitric acid. However, when large pores or cracks appear in the 304 stainless steel coating, they become pathways for corrosive agents to erode the underlying Q345R layer. In both cases: 1. When large holes the size of pinpricks appear in the surface layer, these holes expose the underlying Q345R material, allowing the nitric acid solution to come into direct contact with it. Under the same conditions, due to the poor corrosion resistance of Q345R, corrosion may occur in this area more rapidly. 2. Cracks 10 centimeters long appear in the surface layer: If these cracks penetrate the surface layer, it allows the nitric acid solution to come into direct contact with Q345R, thereby initiating corrosion in the area where they meet. Compared to a pinhole, a crack may create a larger contact area, but whether it will lead to faster corrosion depends on the width and depth of the crack as well as the extent to which it exposes the underlying layer. Generally speaking, a larger exposure area means a higher risk of corrosion. Therefore, if the exposed area of the pinhole is relatively small, while a crack results in a larger area of Q345R being exposed, then in nitric acid solution, the crack may lead to corrosion penetration and leakage more rapidly. However, which specific defect leads to faster corrosion also depends on other environmental factors such as the concentration, temperature, and fluidity of the corrosive medium. The best approach is to conduct tests and evaluations based on the specific circumstances, and to discuss the necessity of repair or replacement in light of the actual application environment of the composite panel. If possible, these defects should be repaired to prevent further progression of corrosion. .

Under such conditions, first, carbon steel is not resistant to nitric acid corrosion, while 304 stainless steel is generally corrosion-resistant； Secondly, if there is a problem with the surface layer (304), in nitric acid solution, the liquid will reach the surface of the carbon steel and cause corrosion there until leakage occurs.