Fechino Files: Hydrochloric Acid

Steven Fechino

When you start laying brick as messy as my career started, you become familiar with acid cleaners. That was the only thing that actually helped my work. I will never brag about my skills, and for a reason, but masonry cleaners (acids) sure can take work like I produce and make a big difference. To keep the conversation simple, I will discuss Hydrochloric acid based on the masonry industry as hydrochloric acid in a reduced dilution is used in many applications that you can probably even find in small percentages within your home, such as toilet bowl cleaners and metal polishes, concrete cleaners to name a couple. The things I want to mention today are the chemicals, the reason they clean, and a bit about protecting yourself and employees from the dangers of Hydrochloric acids. Hydrochloric acid was discovered in 800 A. D., so it is not a new addition to the chemistry the world knows today.  

Hydrochloric acid (HCL) is poisonous in a much purer state than we will see in a cleaning solution, but here is where I give the bottom line. Hydrochloric acid can be very dangerous to people, surroundings, animals and masonry; do not take it for granted. If the acid in a concentrated form is inhaled, comes in direct contact with bare skin, or if swallowed, it can be fatal. The exposure is one phase of the irritant. The second phase of the irritant can be well after the original contact as the chemical continues to damage bone and, in some cases, tissue.

As a Masonry Cleaner

Ok, hydrochloric acid is acid, but we call it cleaner or detergent in the field. That way, we can use it in more places without folks freaking out. 

Before I continue, here is a primer on alkalinity. pH measures how acidic or basic water is on a scale of 1-14 water is. The abbreviation of pH stands for p- “power of” H- Hydrogen. The range goes from 0 to 14, with 7 being neutral. A pH of less than 7 indicates acidity, whereas a pH of greater than 7 indicates a base. Samples that have a pH of 0 are considered acidic with a high concentration of hydrogen ions; a pH of 7 is a neutral solution sharing equal concentrations of hydrogen ions and hydroxy ions. While pH 14 is basic, this relates to a high concentration of hydroxy ions. The pH scale for our purpose ranges from 1:14; however, the scale is based on a logarithm and can extend in either direction. Again, you can have a pH beyond that, but for most common purposes, pH 0 to 14 covers pretty much every normal product that we will encounter in the masonry industry.

As a masonry cleaner, hydrochloric acid is a great solution for cleaning new installations. Typically, new masonry that has been laid for about two weeks or less should be cleaned. They say up to 28 days, but I feel like sooner is better, but not within 36 hours. This time frame will not be published by any manufacturer, and it is based on what I have experienced living in the South for many, many, many (just had a birthday, had to add a third many) years. Once new masonry has cured and been cleaned, the use of Hydrochloric acid is not recommended again for cleaning the masonry as new staining can then occur. A different cleaning solution would be used to clean atmospheric or biological stains that occur over time. Hydrochloric acid is not the masonry clean all product because many bricks are made with different inert properties, and the Hydrochloric acid can react with the chemicals found in different colored clay bases and surface finishes of certain brick, which will result in staining. 

Muriatic and Hydrochloric Acid

I do not recommend the use of muriatic acid for cleaning masonry; however, when I began my time in the industry, I worked in small-scale residential where my ole’ boss was not familiar with the technology of today. Honestly, back then, we did things as they were always done then, and we would not do today. As a laborer, I would often clean the finished wall with a dilution of muriatic acid and water. I was taught to dilute it about 10:1 and to see how it did. We did this back then to save money and acid for the next job. We did not realize that you could burn the masonry if the chemical was too strong. Depending on how it cleaned the wall, sometimes we would need to add a bit more acid to the bucket; yes, we did the bucket and brush method of cleaning. Another reason we were not quite sure of the dilution ratio is because muriatic acid is packaged in different strengths depending on the manufacturer. It can range anywhere between 14.5 to 30 percent acid with a pH of 1 to 2 on the pH scale and contain iron impurities and water, something I learned years later. Muriatic acid, as purchased by a masonry contractor, is typically and technically a “dirty” hydrochloric acid that has been used in a previous manufacturing process and packaged for resale. Muriatic acid is typically a weaker form of hydrochloric acid because of how it is packaged for the retail market. The largest difference between the two products when in equal strength is the impurities that are present in muriatic acid. Muriatic acid is a common chemical household name due to the many years of availability and use around our industry, swimming pools and the use in the steel mills for many years.

Today, there are professional companies that manufacture the correct products based on the chemistry of the material that you are cleaning. If you clean new construction brick and then look at the cube of brick on the job, the brick companies typically indicate what chemical has been tested to properly and successfully clean the brick on the job. When cleaning new masonry, I do not recommend using a pressure cleaner, no matter what pressure you believe you are using, use a bucket and brush, prewet the wall heavily and over-rinse the wall when you are complete. If landscaping is anywhere nearby, saturate the plants and soil (you can even spread agricultural lime around the plants in severe application cases) as much as possible and do a quick covering with plastic during the short time you are working where chemical exposure is present. Cover the windows with plastic, and you will prevent some of the aluminum frames from possibly becoming damaged. Rinsing walls, use as much clean water as possible; when heavy rinsing is not possible, mix two ounces of baking soda per gallon of clean water, allowing it to dwell on the wall for up to 7 minutes if possible and rinse, brush or sponge with available water. Make sure you do not clean in flip-flops, tank tops and sunglasses. These may not affect you the first time, but sooner or later, they will fail you in the personal protection equipment requirements for this task.

Stay safe out there. It is going icey before we know it, yet another reason for care on the scaffolds.