The South Coast Air Quality Management District (SCAQMD) is the air pollution control agency for Californias Orange County and the urban portions of Los Angeles, Riverside and San Bernardino counties, which have been identified as the smoggiest region of the U.S. According to the districts website, Rule 1144 applies to fluids used in its jurisdiction that evaporate off shortly after use (vanishing oils), that inhibit or prevent metal corrosion (metal protectants/rust inhibitors), or are used during metalworking or metal forming operations (metalworking fluids).

These fluids, virtually all of which contain pollution-causing volatile organic compounds (VOCs), are typically used at steel tube and spring manufacturers, steel mills, aerospace manufacturers, automobile part manufacturers and rebuilders. They are also used at machine shops for broaching, drilling, drawing, heading, honing, forging, milling, stamping, tapping, threading and turning operations.

The Rule was adopted in 2009, and put increasingly tight restrictions on VOCs, staged over three years. The final limits went into effect in January 2012 (see Table 1, page 34).

According to Frank Kroto, Lubrizols global technology manager for metalworking, One consequence of Rule 1144 is that end users must report on the potentially volatile fluids moving through their facilities. Each component in the fluid formulation has a VOC value, and the total value for the formulation is calculated based on the weight percentage of each component. Rule 1144 also mandates the test methods that may be used to gauge the VOC content of each fluid component, plus record-keeping and reporting rules for product purchases.

A Widening Net

The onus falls on individual parts manufacturers and fluid providers in southern California to understand the regulation and manage compliance. The regulation can cause logistics and paperwork challenges as well, said Kroto, because fluid suppliers typically supply products and Material Safety Data Sheets for a broader region such as the U.S., North America or Europe. With this regulation, the MSDS must contain VOC data required only by southern California.

Finally, although these requirements are regional, they have national and even international implications. In the past, southern California has adopted a wide variety of safety and environmental regulations that other states, or the federal Environmental Protection Agency, modify and use as a template for their own regulations, said Jennifer Ineman, North America product manager for metalworking additives at Lubrizol.

In addition to California, Illinois has issued guidance regarding VOCs in industrial fluids. And various states across the Midwest and on the East and West Coasts have adopted VOC-emission regulations.

These regulations will spread, and governing bodies representing the entire U.S. and the European Union will likely adopt similar regulations, Ineman added.

Kroto said, The main focus of the regulatory effort is to reduce or eliminate VOCs in order to improve overall air quality. Also important is the desire to eliminate flash-point concerns, and to minimize adverse health and environmental effects. How successful formulators are in meeting these requirements will determine their ability to market products in the affected regions, he concluded.

Other Market Drivers

Besides regulations, Kroto and Ineman, who are based in Wickliffe, Ohio, identified concerns about productivity and functionality as factors driving the reformulation of rust preventives.

Productivity concerns relate primarily to the ability to remove the rust preventive prior to subsequent processing. Historically, semi-permanent rust preventive coatings, while effective in protecting metal surfaces, have been hard to remove. Removal requires a soak in a hot solvent that itself can contribute to VOC emissions and workplace hazards, said Ineman. Curiously, she added, VOCs generated in the removal process are not regulated – at least not by Rule 1144.

Functionally, the market has indicated a desire to limit the number of additives that formulators have to purchase and stock. Customers prefer to use one additive at different treat rates to provide a range of performance levels and to meet global demands, said Ineman. In addition, the rust preventive should be compatible with a variety of metals and pretreatments. And it should be capable of being applied by a number of methods, including spraying, dipping and rolling.

Manufacturers of metal products essentially want only one thing from rust preventives, said Kroto. Namely, that their products arrive at their destination free of rust or stains. To this end, many end users are demanding salt-spray resistance tests as a bench-mark to evaluate the performance of competing products.

At one time, salt-spray resistance of 24 hours was good enough for most applications. However, today more and more component manufacturing takes place in locations far distant from their points of assembly or sale, said Kroto. So longer-term protection has become a leading concern. But it is a major challenge to produce extreme salt-spray performance while maintaining a thin, nearly invisible film that is easy to remove, he observed.

Acid-fume protection is another desirable feature that indicates a products ability to resist the effects of harsh environments, Ineman added. Also, a number of different alloys are present in a typical production facility, so a rust preventive must be non-staining.

Finally, rust preventives typically are temporary coatings that are eventually removed so the part can undergo additional processing. This has spurred the desire for products that can be removed easily, preferably with water-based alkaline cleaners instead of solvents or abrasives.

Do H2O and Metal Mix?

The function of a rust preventive is to completely coat the part – including cracks, crevices and blind holes – to prevent water from reaching the metals surface and causing rust. It should also leave a uniform film, and when the diluent or carrier fluid evaporates, the remaining film must resist wiping off, fingerprints, etc.

In view of the fact that a combination of metal and water typically causes rust, it may seem counter-intuitive that a water-based formulation could be an effective rust preventive. But Lubrizol has launched a research project to develop a water-based rust preventive that would address all the regulatory and market requirements.

The main advantage of a water-based formulation would be extremely low VOCs. The main disadvantage of a water-based formulation is – the water. The rust preventive must be formulated in such a way that when the water evaporates, there is no chance it leaves behind any trace of moisture that can subsequently rust parts.

Other issues water-based products must address are the potentially longer drying time than with solvent carriers, and the need for heat or forced air to speed drying. Finally, precautions must be taken to avoid packing parts until the water has completely evaporated.

Additional aims of the project, according to Kroto, were that the rust preventive could protect a wide range of metals and be applied with multiple methods. The chemistry also would be easy to clean off compared to solvent-based products, yet cling to surfaces in extreme atmospheres, and eliminate the hazards and costs associated with heavy-metal exposure and disposal.

Ironing Out the Kinks

While water-based products would appear to address a large percentage of the issues identified by the marketplace, a number of concerns must be addressed before water-based rust preventives can be used successfully. Specifically, film weight, surface wetting and drying time for water-based products vary significantly from those of solvent-based fluids, said Ineman.

Conventional wisdom would seem to hold that a water-based product would take longer to dry than a solvent-based film. Why is this? In a solvent-based product, the additives are soluble and adhere immediately to the metal surface, Ineman explained. In a water-based product, the additives are held in a micelle and must break through the micelle before they can adhere to the surface.

However, testing shows that the water-based rust preventive dries in about the same time as the solvent-based film. This means that the additive chemistry has reached the part surface, the film is set and the coated parts can be packed or bundled for shipment or storage, Ineman concluded.

Since most rust preventives are slated for removal before parts undergo subsequent processing, fast, easy cleanability is a critical factor. Kroto noted that the water-based products being developed can be cleaned easily by soaking in a 5 percent solution of industrial alkaline cleaner and water at 50 degrees C. This solution is safer than the solvent-based cleaning agents commonly used.

Testing also shows that an aqueous calcium-based formulation can provide equal or better performance than barium-based products. These materials meet the markets performance requirements as well as Rule 1144 VOC limitations, and can provide salt-spray resistance of greater than 100 hours. Correctly formulated, the performance of heavy-duty and moderate-duty formulations can compare favorably with that of solvent-based rust preventives (Table 2).

Heavy-duty water-based rust preventives could be used on truck and trailer frames, farm machinery, tube and pipe, construction equipment, and wire rope and cable, Kroto suggested. Moderate-duty products would be suitable for parts and equipment shipped overseas, rust preventive prelubes, long-term indoor storage of parts and equipment, and thin-film blank wash.