I worked 8 years as a plant engineer at an Allied Chemical facility where we manufactured sulfuric and hydrofluoric acids from raw materials and refined nitric, hydrochloric and acetic acids into reagent grade acids. As you might imagine every production plant in that facility had to deal with leaks in their pipelines, pumps, digesters, distillation towers, storage tanks and other equipment. In the sulfuric, hydrochloric, nitric and acetic acid plants none of our workers had any significant injuries during my years there. After exposure to these acids, workers could quickly wash themselves off in the safety showers and eye wash fountains that were nearby - although nitric acid has a tendency to turn exposed skin yellow very quickly.
It was a different matter in our hydrofluoric acid (HF acid) plant, where everyone was afraid of exposure to the acid from leaks. That's because of HF acid's extreme corrosivity to human flesh. Whenever I, for example, had to go over to our HF acid plant to get information or take measurements for some design work, I'd stop a few feet from the plant and look for signs of any leaks in the overhead pipelines, pumps and digesters before walking into the plant. I saw or heard of many significant HF acid burns while working there. Unlike all other acids HF acid cannot merely be washed off and neutralized with sodium carbonate or another alkaline solution. The acid has such an affinity for human flesh that it will continue to eat its way deeply into ones tissues. To stop its corrosive action, calcium gluconate must be injected into the tissues at the site of acid exposure. One of our mechanics required several plastic surgical repairs to his face after getting sprayed with HF acid. In an offsite accident the son of our draftsman got very dilute HF acid on one hand while picking up several flasks that another Univ. of Calif. lab worker had rinsed off with HF acid (in some laboratories it's used as a glass cleaner). When he realized what had happened, he washed his hands off with copious amounts of water and soaked them in sodium carbonate solution. That night as his hands continued to burn, he hesitated to inform his father about his exposure. When he did tell his father the next morning, his father rushed him to the office of our facility's doctor. The doc injected the son's hand with a lot of calcium gluconate. The damage had been done though by that time. I saw a photo later of this kid's hand. All the finger tips of his hand were eaten away and boney stubs protruded.
HF acid, fortunately, is only slight corrosive to steel and therefore would not be an appropriate weld etching chemical. With any etching mixture containing fluorides and bifluorides, however, there is a likelihood of some HF acid forming in the mixture. One should utilize rubber gloves, face shield and even rubber rain wear as protection during etching to keep from getting any HF acid, no matter how dilute, on ones skin.
LarryL
