What are the effects of pH and alkalinity on metalworking fluids?
October 31, 2021
What are the effects of pH and alkalinity on metalworking fluids? The pH value of any Metal Working Fluid including cutting fluid, cleaning fluid and water-based anti-rust fluid is the main indicator parameter that reflects whether the working fluid is normal. For different metalworking fluids and different customer applications, the optimal pH value is different. For the same metalworking fluid, there will be slight differences in the pH value under the condition of a certain mixing concentration. The pH value of most metalworking fluids is greater than 7, which is alkaline, generally between 8.5-10.5. There are some special processing fluids, their pH value is close to neutral (working pH value is between 7.0-8.0), and a very few are acidic.
pH and alkalinity have many effects on the characteristics of metalworking fluids, total alkalinity (the amount of acid that reduces the pH of the working fluid to 4.5) and useful alkalinity (the amount of acid that reduces the pH of the processing fluid to 7.5) Both are a key parameter. If the pH value indicates how "strong" the metalworking fluid is, then the alkalinity refers to the ability of the metalworking fluid to maintain a certain pH level. Therefore, pH and alkalinity are interrelated. The effect of pH on metalworking fluids 1. Corrosion: High pH value can provide anti-corrosion protection for ferrous metals. The closer the pH value is to 14, the less ferrous metals will corrode. Non-ferrous metals are amphoteric, meaning that when the pH value rises or falls from 7, the possibility of corrosion increases. The exception is magnesium (Mg), which is not susceptible to corrosion at high pH values. The response of materials like nickel (Ni), chromium (Cr) and cobalt (Co) to the pH value has a lot to do with the specific alloy type. 2. Metal solubility: The performance of metal dissolving into the processing fluid is the same as the law of corrosion (rust). The alkali value can strictly control the amount of metal dissolved into the processing fluid. The alkali value is very important, but it must be suitable for the processing fluid and its specific pH. . 3. Stability of emulsion: For traditional emulsions, increase the pH value of the working fluid and the emulsion particles become smaller. When the pH is lowered, the emulsion particles become larger and easily lead to stratification. The smaller the emulsion particles, the better the wettability and the daily carry-out amount. Less. Large-particle emulsions can improve the lubricating performance of mechanical fluids, but the daily carry-out volume also increases. According to the miscellaneous oil in the tank, adjusting the pH of the working fluid can change the miscellaneous oil resistance or emulsification ability of the metal working fluid. 4. Dermatitis: The farther the pH value of the working fluid is from 7.0, the more likely it is to cause dermatitis. Generally speaking, the pH value of the working fluid is better than 10.5. When the skin is exposed to the lye environment, the alkali in the processing fluid saponifies the oil on the skin surface, making the skin dry and even cracking 5. Propagation of bacteria and fungi: Bacteria and fungi can multiply in any pH value and any environment. When the pH value of the metalworking fluid increases, the reproduction speed of bacteria slows down. Therefore, increasing the pH value can reduce the growth rate of bacteria. However, the growth rate of fungi in metalworking fluids increases under high alkaline conditions 6. Compatibility with machine tools: Extreme pH, whether it is high alkaline or acidic, will cause corrosion of machine tool components. Contact of different metals (aluminum or copper in contact with steel or cast iron) will cause corrosion. At extreme pH values, the elastomer (seal ring, etc.) loses its flexibility. Plastic windows become fragile When using different types of metalworking fluids and processing different types of metals, in order to ensure the best performance of the metalworking fluids, to achieve the longest bath life, the tools are fully lubricated, and the surface of the workpiece has excellent roughness, etc. We recommend that the tanks maintain different pH values.
