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Pros and Cons of Full Synthetic Metal Working Fluids

In previous blogs we’ve discussed advantages, disadvantages, and best applications for the four main metalworking fluid types: Straight oils, soluble oils, full synthetics, and semi-synthetics. In this article, we’ll focus in on full synthetic fluids. Let’s ask – and answer – some questions about these products.

What’s the difference between full synthetics and other types?

Unlike straight oils and soluble oils, full synthetics are not a petroleum-based product. All of the components in a full synthetic MWF are water soluble. Another way full synthetics differ from semi-synthetics and soluble oils is that they form a single solution instead of forming micelles that are suspended in water.

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How and why were they developed?

The price of crude oil began rising significantly in the 1950s. This made traditional oil-based MWFs more expensive. Synthetic lubricants were developed in response to this trend. 

How do full synthetics lubricate and what else do they contain?

You may be wondering what exactly is in these metalworking fluids to provide the lubrication needed for machining metal if they contain no petroleum-based oils. Synthetic MWFs are comprised of polymers and water-soluble lubricants. 

Since they are water-based, they also typically contain corrosion inhibitors as well as biocides to hinder the growth of bacteria. Lastly, each particular product will include specially selected additives for specific applications.

What are the best applications for full synthetics?

Full synthetics are typically used in machining operations that generate significant heat such as high-speed ferrous machining applications where surface speeds exceed 650 ft/min. Because they tend to be very stable, they’re an excellent choice for shops with large central lubrication systems connecting multiple machines. 

What are the advantages of using a full synthetic?

Aside from their heat reduction capabilities, full synthetics tend to be clean to use without misting or significant foaming. They have excellent wetting characteristics, are not affected by hard water, and reject tramp oils and fines. They are generally very stable with a long sump life. Most also have a transparent mix, which makes it easier for the operator to see the workpiece.

What are the issues?

Notice we say “issues,” not disadvantages. With proper care, nearly any vulnerability in a fluid can be accounted for and dealt with.

Concentration control is the foremost issue with these types of MWF. If the concentration falls too low, corrosion control can be compromised; if it is too high, a sticky residue will form inside the machinery and on other surfaces, creating cleanliness and maintenance issues. This residue will also adhere to the workpiece itself, possibly leading to rework and definitely creating a need for additional labor to be spent cleaning the piece.

Full synthetics also have poorer physical lubricity than some other types of MWFs.

Is there a better alternative?

In the 1960s, semi-synthetics were created to offer the best characteristics of full synthetics and soluble oils. New chemical engineering advances have allowed Chemtool Incorporated to introduce a product line which offers the advantages of semi-synthetics, full synthetics, and soluble oils: High lubricity, excellent cooling, biostability, ease of maintenance, low foam, and no sticky residues.

The NuSol™ line from Chemtool is a semi-synthetic which incorporates advanced emulsifiers that allow high viscosity components, making these formulas especially well-suited to modern high-speed operations.

Download the NuSol Product Brochure

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