Boric Acid in the Crosshairs


Boric acid is now listed in Europe as a substance of very high concern, and metalworking fluid manufacturers, with no obvious direct replacement, are facing pressure to supply boron-free products.

Robert Stubbs of Sea-Land Chemical Europe gave an update on boric acid, a popular metalworking fluid component, at the UEIL Symposium on Metal Removal Fluids in Barcelona on Sept. 17.

Fluid formulators turned to boric acid in the 1980s as a replacement, in semisynthetic fluids, for corrosion inhibitors that contained nitrite, Stubbs said. Its positive attributes include good ferrous corrosion inhibition, good pH buffering, and it resists bacterial degradation. Its negatives include residue formation, and it is poor at controlling fungus.

Disposal was the first issue of concern that boric acid raised. It has the potential to cause plant failures, especially for soft fruits, above two parts per million, said Stubbs. Reproductive toxicity resulting from human exposures is a more recent concern.

In the late 1990s, several European countries, in particular France, Denmark and Holland, required restrictive labels on boric acid. At the same time, counter studies also came out. Industry continues to question its human effects, Stubbs noted.

Europes new chemical labeling rules last December brought new labeling requirements for boric acid. Now that it is highlighted on the list of substances of very high concern, it must be noted on MSDS if present at greater than 0.1 percent, Stubbs said.

Industry has responded with improved handling procedures to minimize exposures and by revising formulations, said Stubbs.

The outlook for boric acid is cloudy. While boron-based metalworking fluids will continue for many years, he continued, end users will pressure for boron-free products. Many will avoid handling boric acid if possible.

There are several alternate chemistries, including lactic acid, phenoxyethanol, dicyclohexylamine and alternative cyclic/branched amines, but all have limitations in use, said Stubbs. The pathway to the current situation is extremely flawed, and were concerned that other materials will be restricted without appropriate justification.

I hope companies will develop innovative technology, Stubbs concluded. There is potential for innovation, to surpass boron technology.

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