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Oxalic acid is a chemical substance that plays an important role in many industrial sectors and in households. As a dicarboxylic acid, oxalic acid has numerous applications, especially in the technical cleaning of metals and sanitary facilities. In this blog post, we want to take a closer look at the properties and possible uses of oxalic acid.

Chemical properties of oxalic acid

Oxalic acid, also called ethanedioic acid, is a colorless, crystalline compound with the chemical formula C₂H₂O₄. It belongs to the group of dicarboxylic acids and is characterized by its high solubility in water as well as its strong acidity. The pKa value of oxalic acid is 1.23 for the first dissociation stage and 4.19 for the second dissociation stage, making it a comparatively strong acid.

Besides its solubility in water, oxalic acid is also well soluble in ethanol, methanol, and other polar organic solvents. Thermally, oxalic acid is stable up to about 101°C before decomposing with the release of carbon dioxide. This property is utilized by the industry in the production of formic acid.

Technical applications of oxalic acid

The versatile properties of oxalic acid make it a valuable aid in technical cleaning. Oxalic acid is widely used especially in the following areas:

Metal cleaning and descaling

Oxalic acid is an effective agent for removing oxide layers (rust, scale) from metal surfaces. It reacts with metal oxides to form soluble metal oxalates, which can then be easily rinsed off. Oxalic acid has proven especially effective in cleaning steel, iron, and copper.

Cleaning of sanitary facilities

Lime deposits in toilets, faucets, and showers can be effectively removed using cleaners containing oxalic acid. The acid dissolves the lime compounds and leaves a clean, shiny surface.

Removal of rust stains

Oxalic acid is excellent for removing stubborn rust stains on textiles, tiles, or other surfaces. Through its reducing effect, it converts iron oxides into soluble iron oxalates, which can then be easily rinsed off.

Pickling processes in the metal industry

In the metal industry, oxalic acid is used as a pickling agent. The acid is used to remove oxide layers, scale, or welding residues from metal surfaces to achieve optimal surface preparation for subsequent coating or finishing processes.

Wood treatment

Oxalic acid also plays an important role in woodworking. For example, it is used to remove iron stains on wood surfaces or serves as a base for special wood stains.

Further applications

In addition to the main applications mentioned, oxalic acid is also used in many other areas, such as textile cleaning, ceramic cleaning, electronics industry, or electroplating.

Safety aspects when using oxalic acid

Although oxalic acid is a useful and versatile cleaning agent, caution must be exercised when handling it. Oxalic acid is toxic and can be harmful if swallowed or in contact with skin. Therefore, appropriate protective measures such as gloves, safety goggles, and good ventilation are always required when handling products containing oxalic acid.

Furthermore, oxalic acid is not suitable for all materials due to its corrosive effect. It can attack sensitive surfaces such as aluminum, brass, or galvanized steel. In such cases, alternative cleaning agents must be used.

Conclusion

Oxalic acid is a versatile and powerful helper in technical cleaning. Its ability to effectively dissolve metal oxides and lime deposits makes it a valuable tool in numerous industrial sectors. However, handling oxalic acid requires special safety measures due to its hazardous nature. With the right application and protective equipment, oxalic acid can be excellently used for a variety of cleaning tasks.