Beyond Rust Inhibition: How TEA works in metalworking fluids?
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Triethanolamine (TEOA or TEA) is a key additive in water-based cutting fluids. Most cutting fluids contain TEA, but what role does TEA play in cutting fluids?
The functions of Triethanolamine (TEA) in water-based cutting fluids.
As a component of Synthetic Water-Soluble Oiliness Agents by Reaction with Oleic Acid
Currently, most oiliness agents with excellent lubricity are long-chain fatty acid and are generally insoluble in water.
Oleic acid, an important fatty acid, is insoluble in water. However, triethanolamine oleate (TEAO), produced by reacting oleic acid with triethanolamine, is water-soluble.
Triethanolamine oleate (TEAO) is a commonly used water-soluble oiliness agent. When added to cutting fluids, it readily forms a physical adsorption film between the cutting bit and the chip (workpiece), providing lubrication under low loads. Combining TEAO with extreme pressure additives can also provide a synergistic anti-wear effect, further improving cutting performance.
TEA as a Rust Inhibitor in Water-Based Systems
Basic Rust Inhibition:
TEA itself is an effective water-soluble rust inhibitor for steel.
At a typical treat rate of 0.5-2%, it provides good short-term rust prevention.
Synergistic Rust Inhibition:
TEA exhibits strong synergistic anti-rust effects when combined with other water-soluble inhibitors.
Key synergistic partners include Ternary organic polycarboxylic acid (L190), sebacic acid, and boric acid. They significantly enhance the overall rust prevention performance of water-based cutting fluids.
Copper Corrosion Solution:
Copper corrosion can be effectively controlled by adding 0.1–0.3% of water-based metal activator (Chorus Metal Deactivator TTA-42) to formulations containing TEA.
Derivative Inhibitor:
Triethanolamine oleate (the reaction product of TEA and oleic acid) is also a good rust inhibitor, which is suitable for protecting both ferrous metals and aluminum alloys.
TEA as a Surfactant in Water-Based Systems
In water-based cutting fluids, TEA acts as a surfactant with four key functions:
1. Penetration – Helps the fluid soak into the cutting/grinding zone.
2. Dispersion – Spreads additives evenly throughout the fluid.
3. Stabilization – Keeps oil-water mixtures (emulsions) from separating.
4. Cleaning – Flushes away metal chips and debris.
TEA is essential in synthetic cutting fluids and emulsions. Improving wetting and penetration at the tool-workpiece interface, ensures water-based fluids can fully deliver their cooling and cleaning power during machining.
Stabilizer in Water-Based Cutting Fluids
Some of the Lubricants and EP (Extreme Pressure) additives in water-based cutting fluids can break down in water ("hydrolyze") and stop working effectively.
Adding a small amount of Triethanolamine (TEA) acts as a stabilizer.
e.g., Organic borate esters are newer EP/anti-wear additives made by reacting boric acid with alcohols/polyols. Their main weakness is that they easily break down in water (hydrolyze). Adding a little TEA during their production helps prevent this breakdown.
A classic formula of water-based cutting fluid with TEA
| Component | Example Ingredients |
| Base Fluid | Deionized Water |
| Alkalinity Reserver | Triethanolamine (TEA) |
| Lubricant/Emulsifier | Triethanolamine Oleate |
| Extreme Pressure (EP) Additive | Sulfurized Compound, Phosphate Ester |
| Rust Inhibitors | Organic Polycarboxylic Acid + Sebacic Acid +Boric Acid |
| Metal Deactivator | TTA-42 |
| Biocides | BIT (Benzisothiazolinone), BBIT (Butyl BIT) |
Precautions for Using TEA
1. Avoid Mixing with Nitrites
Never add sodium nitrite rust inhibitors to TEA-based cutting fluids. Triethanolamine (TEA) reacts with nitrous acid (from nitrites) to form harmful substances that pose health risks to workers. Always choose alternative rust preventatives compatible with TEA.
2. Managing Odor
When used in metalworking fluids, TEA sometimes emits a mild, unpleasant odor. You can either reduce the amount of TEA in the formula or add a very small quantity of fragrance to mask the odor.
3. Not for Carbide Tools
Do not use TEA-containing fluids when cutting or grinding carbide tools. Water-based TEA solutions can slowly dissolve cobalt, a key binder in carbide tools. it may weaken the tool's strength, reducing its cutting performance and shortening its life.
