When hot steel is worked above their recrystallization temperature, oxygen will react with the outside layer of iron as it cools from its molten state, resulting in a flaky layer of scale. This is often visible as rust, or iron oxide, but there are many other known allotropes of iron oxide as well. It is difficult to work with the steel when it has this layer, and also makes it inconducive to painting.

To solve this issue, the steel is pickled, which is when the metal is dipped into a solution to remove the surface impurities before further processing such as rolling or galvanizing. Using hydrochloric acid in pickling provides bright surfaces.

Oil and gas operators have relied on acidizing to improve well productivity for over a century. Acidizing is one of the most effective ways operators can improve the productivity of a well, both the initial productivity upon drilling as well as to restore productivity by essentially cleaning out the scale (ie. calcium carbonate), rust, and other debris that may be restricting flow in the well. A well’s formation type will affect the type of acid used in this process, though hydrochloric acid is most commonly used.

High fructose corn syrup (HFCS) is an artificial sweetener derived from corn that first become popular in the 1970s when sugar prices were high but corn prices were low. For decades it has been used in the US to sweeten processed foods and soft drinks. Similar to sugar, HFCS is composed of both fructose and glucose. To manufacture HFCS, producers take corn starch, which is composed of glucose molecules of infinite length, and consists of amylose and amylopectin, apply heat, caustic soda and/or hydrochloric acid plus the activity of three different enzymes to break it down into the simple sugars glucose and fructose.