Hazmat IQ Corrosives

BY STUART WEST, CAPTAIN, FIRE INVESTIGATIONS

One of the most common products involved in Hazardous Materials incidents, aside from incidents involving flammable liquids, are corrosives. Corrosives are most often encountered in either liquid or gaseous states but can also come in solid form.

Typically, a corrosive material can be defined as a liquid or a solid that causes full thickness destruction of human skin at the site of contact within a specific period, or a liquid that chemically reacts with steel or aluminum surfaces. In the ERG, corrosives are found as a class 8 in guide #153 and are usually transported in a #407 or a #412 road trailer. Corrosives can be either acids or bases and the strength of their corrosive properties is measured on the “pH scale”. Acids can be further described as being substances that generate hydrogen ions (H+) in water, whereas bases generate hydroxide ions (OH-) in water. Acids react with active metals, such as magnesium, to produce hydrogen gas. Some metals, such as potassium, lithium and sodium, will react explosively when contacted by acids. Acids have a sour taste (do not test this out) and will also conduct electricity. This is why sulfuric acid is commonly used as an electrolyte in car batteries. Bases, on the other hand, have a bitter taste.

They have a slippery, soapy texture and will also produce hydrogen gas when contacted with some metals. Sodium hydroxide (lye) is used in soap making.

If you do a “Google” search, you may find a couple of different answers on what the acronym pH stands for. Some say it stands for “power of hydrogen” and others claim it stands for “potential of hydrogen”. Most people are somewhat familiar with the pH scale but there are some important points to remember when discussing it. As you may recall, the pH scale goes from 0 to 14, with 7 being neutral. 0 to 6 is the acidic side, with 0 being the strongest acid. Conversely, 8 to 14 is the basic side, with 14 being the strongest base. Basic substances are also sometimes referred to as alkaline or caustic. It is also important to take note that the pH scale is a “logarithmic scale”. This means that the difference between numbers on the scale is a ten-fold increase or decrease in corrosiveness, depending on which direction you are moving on the scale. For example, the difference between an 8 and a 12 on the pH scale is in fact a difference of 10,000 times in alkalinity! This distinction becomes ever important when deciding if “neutralizing” a spill is a valid option.

If two substances are mixed that are too far apart on the pH scale, the reaction will be violent and exothermic (heat producing), with liquid splashing and sputtering. Obviously, this is not a desirable outcome. It is also important to keep in mind that for most corrosive liquid spills, the amount of neutralizing agent required to bring the pH within a desirable range would be too great. Therefore, on most occasions, containment of a larger spill is most practical. Keep in mind that it is of utmost importance to prevent any product from entering the water system. It is imperative that spills be dealt with promptly. Depending on the substrate that the spill is on top of, the product can begin to seep into the substrate. This is more of an issue when the spill is on top of a very porous substrate material. Smaller spills can typically be dealt with by using absorbent materials that do not cause an adverse reaction with the product.

Anyone working near any product, will be a Hazmat Technician or partnered with one and wearing full PPE, including SCBA. Most times, a “Level B splash suit” that has been selected after doing the appropriate product specific research will be sufficient protection. Most acids that may be encountered do not have the ability to move away from the spill area in vapour form. This is because they typically have extremely low vapour pressures; consequently, they do not have the ability to “reach out and touch you”. However, this information is all part of the product specific research that will be done by the Hazmat team and is not something that we guess at or assume. If there are any doubts, a “Level A” suit may need to be selected. Most times a “Level B” suit is preferred, as it is a much better suit for performing work. Wearing a “Level A” suit would be seen as a last resort, as it limits the ability to perform work in terms of dexterity, as well as in terms of shortening work cycles, due to heat and physical exhaustion concerns.

Every truck with a multi gas detector, also has pH paper. Any product encountered should be checked to determine the pH. Prior to contacting the liquid with the paper, the pH paper should be waved over top of the liquid. Any colour change in the paper is an indication that the product has a high vapour pressure and therefore, the vapours are capable of travelling away from the origin of the spill. This information will affect hot-zone delineation and will also factor into where the cold zone and decontamination zones are set up, with wind direction being of prime importance. Determining the pH is a crucial step at any Hazmat call, in order to identify the risks that are associated with any unknown product. We deal with corrosive products in everyday life. Understanding the pH scale and corrosive properties can help us make informed decisions when faced with these products at an incident, whether it be a road trailer that has had a container breach, or at a spill at an industrial facility. Remembering how the pH scale works may well assist crews in determining what the dangers are. Stay safe.

One of the most memorable scenes from the movie fight club is when the character Tyler Durden, played by Brad Pitt, licks the back of actor Edward Norton’s hand and then proceeds to pour sodium hydroxide (lye) directly on his skin. In the ensuing moments, Edward Norton writhes in pain as the chemical proceeds to eat away at his flesh. Tyler Durden then remarks about how he could pour water onto Edwards hand and make the burn worse, or he could pour vinegar onto the wound, thereby neutralizing the chemical and ending his pain. The scene ends with Tyler Durden pouring vinegar onto the wound much to the relief of Edward Norton.

The question is, was this little chemistry demonstration accurate? The answer is no. Pouring vinegar, directly onto skin that is already damaged would only cause further pain and injury. In fact, having a neutralization reaction, which creates heat, occur directly on one’s skin, is a terrible idea. Copious amounts of water would have been a much better option. However, the scene was very convincing and well done. It’s not often you see chemistry played out in a Hollywood blockbuster!