Hapemaisuus

Hapemaisuus is a Finnish term that refers to the susceptibility of a substance to oxidation, i.e., its tendency to lose electrons or form oxides in the presence of an oxidizing agent such as oxygen. In practice, hapemaisuus describes how readily a material or compound undergoes oxidation under specified conditions.

The concept is used across disciplines including chemistry, materials science, environmental science, and food science. It helps explain phenomena such as corrosion, degradation of polymers, chemical stability, and shelf life of foods and fuels. Hapemaisuus is related to general chemical reactivity but is often discussed as a more specific tendency toward oxidation.

Factors influencing hapemaisuus include electronic structure, the presence of stabilizing or destabilizing groups, protective oxide layers or coatings, moisture, temperature, pH, and the presence of catalysts or electrolytes. Material properties such as crystal structure, microstructure, and surface condition can also affect oxidation tendency.

Measurements and indicators are typically indirect and include redox potential, oxidation rate, corrosion rate, or induction periods in aging or accelerated aging tests. Common examples illustrate the concept: iron oxidizes readily in moist air, leading to rust; aluminum forms a passive oxide layer that lowers its practical hapemaisuus; certain polymers oxidize over time, causing embrittlement; foods and fuels can undergo oxidation, resulting in rancidity or spoilage.

Etymology and relation: hapemaisuus derives from happe (oxygen) with the suffix -maisuus, forming “the quality of being related to oxygen.” In Finnish literature, it is sometimes used interchangeably with hapettuvuus (oxidizability) or hapettuminen (oxidation), though some authors reserve hapemaisuus for the intrinsic tendency and hapettuvuus for measured rates. See also hapettuminen, hapetus.