Selection of piezoresistive diaphragm material

Advantages of titanium diaphragms: Exceptional corrosion resistance: Titanium is a highly chemically active metal that exhibits excellent resistance to many corrosive agents, including seawater, chloride ions, most oxidizing acids, and organic substances. Under your operating conditions, with the presence of highly corrosive substances such as chlorine and sodium hypochlorite, titanium can maintain its performance and structural stability over the long term. Good mechanical properties: Titanium not only has strong corrosion resistance but also possesses good mechanical properties such as high strength and toughness, enabling it to withstand certain levels of pressure and impact. Surface self-passivation ability: Titanium reacts with oxygen to form a strong and dense passive oxide film on its surface. This film remains very stable in most corrosive environments, and it can repair itself even if damaged. Advantages of 316-lined PTFE diaphragms: Excellent corrosion resistance: PTFE can resist the erosion of almost all organic and inorganic compounds, including strong acids such as aqua regia and strong bases such as concentrated sodium hydroxide. Under your operating conditions, corrosive substances such as sodium hypochlorite have little impact on PTFE. Wide operating temperature range: PTFE can operate stably in high and low temperature environments ranging from -200°C to +250°C, meeting the requirements of normal temperature conditions. Anti-aging, leak-proof, long lifespan: PTFE material possesses excellent anti-aging properties and is not prone to leakage, which helps to extend the service life of the diaphragm. Considerations regarding media that are not applicable: Although PTFE has excellent corrosion resistance, its performance may be affected under certain extreme operating conditions. However, under your operating conditions (room temperature, slight negative pressure, involving water and chlorine, sodium hypochlorite), the corrosion resistance of PTFE is usually sufficient to handle the situation. It should be noted, however, that if certain special ions or compounds are present in the medium, they may react with PTFE or affect its properties, but this is relatively rare in your operating conditions. In contrast, titanium exhibits more extensive and stable corrosion resistance, being hardly affected by the type of medium (except in a very few extreme cases). Therefore, from the perspective of corrosion resistance, titanium diaphragms may be more reliable. Conclusion Under your operating conditions, both titanium diaphragms and PTFE-lined 316 diaphragms can theoretically meet the corrosion resistance requirements. However, given the broader and more stable corrosion resistance of titanium, as well as its excellent mechanical properties, it may be safer to choose a titanium diaphragm. Of course, the specific choice still needs to be determined by taking into account factors such as the actual application scenario and cost budget. As for whether there are operating conditions where no suitable medium is available (excluding permeable media, and only corrosive media are considered), generally speaking, under normal chemical processing conditions, both titanium and PTFE can handle most corrosive media. However, when selecting materials, a detailed analysis is still required based on factors such as the type, concentration, and temperature of the specific medium, to ensure that the chosen materials can meet the requirements of the operating conditions.

Materials made of 316+PTFE or 316+PFA are better

For such operating conditions, a diaphragm made of titanium is a suitable choice, as long as the initial operating environment is not dry chlorine. If a tantalum diaphragm is chosen, the price will be a bit higher. 316 + PTFE membrane is also an option, but the bonding of the PTFE membrane must be reliable; once the PTFE membrane is damaged or any medium seeps onto the 316 diaphragm, it will quickly corrode the 316 diaphragm. Titanium diaphragms may cost only a little more than 316 + PTFE diaphragms, but they eliminate the hassle of installing the diaphragm and carrying out subsequent maintenance