The pressures that metalworking fluids marketers face are familiar to those of many other lubricants. End users want fluids to work in hotter, harsher environments with smaller sumps and longer drain intervals. They also they want less waste and for that waste to be less harmful.

Hotter operating temperatures come from faster tool speeds, while harsher environments come from newer tool surfaces, such as harder alloys or ceramics. These applications require better cooling, so water-based fluids are the preferred approach since water has much better heat transfer characteristics than mineral oil.

Minimum quantity lubrication, which unlike flooding the working area with lubricating coolant, coats the tools and the workpiece with a lubricant film that reduces heat by reducing friction, may require drastically different formulations from those currently employed. Meanwhile, developments in 3D printing, material deformation and dry machining require no lubricant, reducing the size of the overall market and income from fluid sales that can fund further research into new products.

The perfect storm begins to pick up when legislation, such as the European Chemicals Agencys Biocidal Products Regulation, severely restricts most of the effective biocides that protect water-based fluids from the wide variety of bacteria that contribute to biofilms, toxins, odors and emulsion stability.

The global metalworking fluid market could reach an annual volume of 3.65 million metric tons and be worth U.S. $14 billion by 2025, up from $10.75 billion in 2018, according to a report by Grand View Research.

Irreconcilable Requirements

The scenario is compounded by the apparently irreconcilable nature of market demands, one conference speaker noted. Customers want products that last a long time, but most biocides that release formaldehyde have been classified as class 1b carcinogens under the BPR and must carry a hazard warning sign.

In addition, machine shops want soluble oils that form stable emulsions, but many emulsifiers are highly biodegradable, so susceptible to bacterial degradation. While formulators have many options for both emulsification and lubricity, the surface-active components that provide those effects can promote foam as the fluid ages or if water hardness (the degree of calcium and magnesium found in the local water supply) changes.

Current componentry is often derived from natural products with good biodegradability. Petrochemical replacements are, by definition, not natural products. Enhanced resistance to biodegradation means that the fluids will persist longer as waste. Both trends run counter to the sustainability aspirations of many major customers and original equipment manufacturers.

Supply Drought

Taking a broader perspective, several countries that have extensive metalworking industries are predicted to suffer from high water stress by 2040, whereby access to water will become severely limited. The high risk countries include Italy and Ukraine, with their extensive and differing metalworking industries. The risk for Spain, Turkey, Greece, North Africa (except Egypt), the Middle East, India and Pakistan is extremely high. When this is coupled with a projection that water usage for manufacturing will grow by 40 percent up to 2050, according to the Organization for Economic Cooperation and Development, there are major issues to face for the metalworking fluids industries and their suppliers.

Oil-based fluids do not offer a simple solution. Apart from the thermal problem mentioned previously, they have their own health, safety and environmental issues associated with inhaling oil mists, as well as hygiene and slip hazards that result once they are deposited on surfaces.

However, the BPR has been the biggest issue of late and is possibly the biggest ever for metalworking fluid formulators. Under the regulation, all materials that are classified as formaldehyde releasers – which are not necessarily all fluids that release formaldehyde – must carry the H350 Hazard Statement code in Europe and a serious health hazard warning sign, which means that these fluids are effectively banned in German machine shops, for example.

Layered on top of these are the recent losses of boric acid and the ever-lengthening lists of substances restricted by automotive and aerospace OEMs. These, according to one industry insider, start with substances on the ECHAs Restriction, Evaluation and Authorization of Chemicals Regulation as the baseline for protecting their staff and then build up to their grey, red and black lists with substances that may not be harmful to health but have an impact on corporate reputations.

Many of the available materials that have biocidal properties are fungicides, but not bactericides. This means that they are suitable for protecting fluids during tank storage but not for formulating concentrates.

Changing Business Models

Others in the industry have appealed for change to current business models, stating that companies had to stop treating everything as a secret. Proposals include more collaboration between end users, metalworking equipment and tool suppliers, machine shops and fluid suppliers.

Two changes that would require collaboration across the industry include adding preservatives at the machine shops and accepting shorter fluid lifetimes. The former is feasible but requires that staff be trained or that there is an automatic dosing system. Both may be attractive to larger customers, but smaller companies may not be able to absorb the costs of either consequence. Accepting shorter fluid lifetimes would mean more waste, which could require downstream users to change the sustainability requirements they place on their suppliers.

Another proposal was whether it is possible to authorize formaldehyde releasers under REACH for use in different metalworking applications, but that requires customer, and probably trade union, agreement.

There are some limited formulating options in the biocidal space. Not all chemicals that release formaldehyde have been categorized as formaldehyde releasers and have not been identified as carcinogenic, so do not warrant application of the Globally Harmonized System of Classification and Labelling of Chemicals H350 hazard code. One example is ethylene glycol bis(semiformal), known also as (ethylenedioxy)dimethanol or 1,2-Bis(hydroxymethoxy)ethane. This is only classified as a skin irritant and capable of causing serious eye damage. This may have a lifetime of five years before the ECHA reviews its categorization. However, it cannot be used with other formaldehyde releasers, as that will trigger the H350 hazard code.

Other options have been proposed. It is possible to formulate with combinations of up to three current biocidal components below their new individual thresholds and avoid the H350 hazard code. However, performance is expected to be compromised. One specific obstacle, according to one speaker at the conference, may be the strains of bacteria that are specific to individual machine shops, which require unique combinations of biocidal additives. Dual-use additives – such as amines that are primarily corrosion protectives – also have some biocidal properties, so are being investigated by all players in the market.

Although not necessarily revolutionary, developments include irradiation of fluids by ultraviolet light. This may be possible in synthetics, but soluble oils are not transparent to UV light. Several players are screening molecules from the personal care and surface coatings industries that have similar effects.

It is impossible to predict which option might be successful. If one or two are unsuccessful, then a lotof business is going to change rapidly, particularly in Europe. If all are unsuccessful, it could well be the end of metalworking fluids as we know it.

Trevor Gauntlett has more than 25 years experience in blue chip chemicals and oil companies, including 18 years as the technical expert on Shells Lubricants Additives procurement team. He can be contacted at trevor@gauntlettconsulting.co.uk