Regarding Triethanolamine

Question:

I have a question regarding use of Triethanolamine (TEA) in cleaners. I read your reply in PF Online. You had mentioned that TEA provides in-process rust prevention for steel parts. Could you please explain this? Also, I have read articles referring to TEA as a water-repellent and I don’t quite understand that either. P. T.

Answer:

I believe there are two factors that contribute to the rust prevention that is experienced with triethanolamine. First, I believe some of the protection is gained from the residue being slightly basic. That pH region is generally good to minimize corrosion attack. The more extremes of pH will tend to generate more attack of the base material resulting in a higher corrosion rate.

The second reason I believe is due to the polar structure of the molecule. Generally, polar molecules that are formulated into cleaners and lubricants tend to have the polar end adsorbed to the metal surface while the nonpolar end is oriented away from the surface. As the chain length of the molecule grows, it tends to be more hydrophobic (water repelling) and as such can act as a better water repellent.