Everything You Need to Know About Chloride and its Effect on Metalworking Lubricant Performance
In manufacturing facilities, maintenance teams often face persistent challenges with increased wear, corrosion, and damage to machinery, such as machine tools, work-pieces, and piping. Despite regular cleaning, lubrication, and routine maintenance, these issues can continue—especially when metalworking fluids are heavily used. One common but often overlooked cause of these problems is chloride contamination in the metalworking fluids.Table salt—sodium chloride—may make our food taste better, but when it comes to metalworking fluids, we need to maintain a low-to-no salt diet to help prevent corrosion.
In this article, we’ll explore how chloride contamination can negatively impact metalworking lubricant performance and discuss the proactive steps you can take to control corrosion, enhance lubricant performance, and avoid critical equipment failures.
What are Chlorides and How Do They Cause Corrosion?
Chloride ions (Cl-) are negatively charged particles that come from the element chlorine. High concentrations of chlorides can significantly increase the potential for corrosion in metalworking systems. Chlorides break down the passive oxide film that normally protects steel surfaces, exposing the metal to oxidation and rust formation. These ions also interact with other contaminants in the environment or the metalworking fluids, accelerating the corrosion process.
What Factors Contribute to Chloride-Induced Corrosion?
Chloride-induced corrosion in metalworking systems is heavily influenced by the system’s design, fluid type, and maintenance practices.
Chlorides are commonly found in water-based metalworking fluids. Water sources, particularly those with sodium chloride or chlorinated compounds, are a significant source of chloride contamination. Chlorine is also commonly added to water supplies for sterilization and disinfection purposes. When water-based fluids are used in cooling systems, evaporation can increase chloride concentration, which leads to corrosion in tools, machine components, and cooling system parts.
Many lubricant companies still use chlorine-containing additives to improve the performance of metalworking fluids but some are more harmful than others. For example, FUCHS uses patented chlorinated paraffin technology that is specially designed to minimize chloride concentrations in metal working fluids.
Oil rejecting components, often found in biocides, are designed to prevent bacterial or fungal growth that can lead to fluid degradation. While these constituents can contribute some organo-chlorides to a system, they are far less reactive than chloride ions contributed from other sources.
Poor fluid circulation or stagnant fluid in low-flow areas can lead to the accumulation of chlorides, exacerbating localized corrosion. Inadequate filtering, drainage, or de-watering can increase the risk of rust and corrosion due to depleted inhibitors and changes in pH, particularly in sensitive components like tooling, threaded parts, and cooling systems.
Environmental factors like humidity and temperature variations can further contribute to chloride concentration, while operational conditions like high temperatures or long cycles between fluid changes may increase the risk of buildup.
What Can I do to Mitigate the Effects of Chlorides?
Controlling chloride contamination is essential for maintaining the performance of metalworking fluids and the integrity of your machinery and work-pieces. Below are effective strategies for reducing the impact of chlorides in metalworking systems:
Using treated water like deionized (DI) or reverse osmosis (RO) water can reduce chloride contamination in water-based coolants. Always test the water quality for chloride levels, especially when mixing coolants, and implement regular monitoring to avoid high chloride concentrations. It is also important to be mindful of potential seasonal fluctuations, especially during the summer months.
Selecting chloride-free or low-chloride metalworking fluids is a critical step in mitigating chloride-induced corrosion. Incorporate additives like corrosion inhibitors that stabilize the fluid, resist degradation, and combat chloride contamination. Ensure that the fluid concentration falls within the manufacturer’s recommended range to avoid over-dilution, which can reduce the fluid’s effectiveness, or over-concentration, which can increase corrosion and chemical breakdown.
To prevent corrosion, it’s essential to maintain a stable alkaline pH in metalworking fluids, typically between 8.5 and 9.3. Chlorides are more corrosive in acidic conditions. The use of an alkaline buffer raises the pH and creates a more stable environment that helps protect the metal surface by reducing the ability of chlorides to react with it. Regularly test and adjust the pH of your metalworking fluids to stay within the optimal range.
Filtration systems help remove reactive metal fines and swarf that exacerbate corrosion in the presence of metal working fluids with high chloride concentrations. Temperature control and regular fluid replacement are also vital to prevent the buildup of chloride concentrations over time. Consistently clean and replace filters to ensure your system remains free of corrosive contaminants.
Mitigate Chloride Contamination with FUCHS
Chlorides can present a significant challenge to the performance and lifespan of metalworking equipment. Increased understanding of their sources and potential maintenance strategies can allow for proactive mitigation of their effects. By implementing these strategies, you can protect your equipment, enhance your metalworking processes, and reduce costly downtime and repairs over time.
FUCHS offers advanced, chlorine-free metalworking fluids that reduce the risk of corrosion while improving the performance of your equipment. Our products, such as RENOFORM 930S, are formulated with alkaline buffering to help protect against chloride-induced corrosion. We also offer expert services and training to help you optimize your fluid management and maintenance practices.