Fechino Files: Hydrofluoric Acid

Steven Fechino

Every month, I try to take a common subject that relates to all of us in the masonry trade. I try to simplify it and sometimes define parts that, if you are older like me, well, honestly, maybe you just forgot the details.

Last month, I discussed Hydrochloric acid that is commonly used for cleaning masonry, but in a much-diluted form. This month, I will discuss Hydrofluoric acid, commonly used as a masonry restoration detergent.

Hydrofluoric acid will be discussed as a chemical, the severity of improper use of the product and proper use of the products we use. In both of my articles, I simply discuss the chemicals, and in no way am I suggesting that the reader shy away from using the proper products designed by reputable manufacturers to clean masonry.

Hydrofluoric acid is made by combining hydrogen fluoride (HF) into water. Hydrochloric acid and Hydrofluoric acid are dangerous; personal protective gear should ALWAYS be used. Hydrofluoric acid is actually more dangerous to human tissue. In the state where we use both acids, understanding the jobsite conditions, surroundings and application instructions can provide the experienced mechanic with what they need to know for the safe use of the product. Wind, vegetation and veneer material protection, as necessary, all lead to a successful use of the acid. 

Hydrofluoric Acid as a Raw Chemical

Hydrofluoric acid, HF, as it is found on the periodic table, has many uses outside of masonry. It can be used in manufacturing many products that are unrelated to the masonry trade. In a concentrated form, Hydrofluoric acid does not have a color and, as a contact poison, is very corrosive. When Hydrofluoric acid contacts the skin, it will penetrate tissue. HF can find exposure into the body through eye contact, inhalation, swallowing or contact with skin. The damage that occurs when the body contacts Hydrofluoric acid is not necessarily instant; it can be slow without symptoms, which can also lead to a more severe illness. When exposure occurs, medical treatment should be made available as soon as possible. Contact with Hydrofluoric acid can interrupt nerve function and, in severe cases, react with the calcium in the blood. The deterioration of the calcium can lead to cardiac arrest.  

The typical use of Hydrofluoric and Hydrochloric acid in our industry is to clean masonry walls. Very seldom do we just clean walls that are four feet tall; therefore, here are a few lessons I learned and a few tricks that can help you out. Always wet the wall wetter than you need to; it will absorb into the masonry on a very hot day, and the extra water on the surface of the masonry will make cleaning more productive and allow you to rinse or neutralize the cleaner much easier as it will clean the surface stains more efficiently. As a younger me, I thought that the chemical directly on the stain would clean it better, but I was so wrong in this belief.

When cleaning in congested areas, as much as possible, just use water, if possible, for the first day or so. Once, we had a lady actually say we ruined her paint because of the cleaning acid on her car that was parked in a lot near where we were working (very close). She was upset when she found out from the superintendent that we were using water, and it was not our fault. 

Another lesson I learned by doing the bucket and brush method from a pipe frame scaffold is not to overfill the bucket and wire or strap the bucket to the scaffold jack; if you do not do this, sooner or later, you will be mixing up another batch before you know it. As much as possible, store your used washed-out brushes in a bucket of clean water; they will last quite a while and keep you working on rainy days doing wash down. All of the manufacturers that formulate cleaning detergents offer cleaning instructions, and they will outline where to start and where to rinse the wall. Follow these instructions as they will make you money.

Bottom line, if you or an employee ever get splashed with a diluted restoration detergent such as Hydrofluoric acid or Hydrochloric acid, get medical attention as soon as possible, as the reaction may not be immediate, but it may still be severe. Be safe, not sorry.