corrosiveness

Corrosiveness is the property of a substance to degrade or damage materials, especially metals, through chemical reactions or electrochemical processes. It encompasses chemical corrosion, driven by reactions with the material, and electrochemical corrosion, driven by redox reactions that require an electrolyte and electric current. Substances with high corrosiveness include strong acids and bases, oxidizers, and certain salts; environmental conditions such as moisture, heat, and oxygen influence the extent of corrosion.

Mechanisms and factors: Chemical corrosion depends on reaction with the environment; electrochemical corrosion requires an electrolyte and electron transfer, often via galvanic couples or localized attack such as pitting, crevice corrosion, or intergranular attack. Key factors are material type, surface condition, temperature, humidity, pH, and the presence of aggressive species such as chlorides or sulfates. In the atmosphere, metals like iron corrode in moist air to form oxides such as rust.

Measurement and indicators: Corrosion rate is commonly expressed as thickness loss per year (mm/year) or mils/year, derived from weight loss or electrochemical methods such as polarization resistance. Visible signs include surface roughening, discoloration, pits, and thinning. Some corrosive substances pose safety hazards to skin and eyes, requiring appropriate containment and personal protective equipment.

Prevention and mitigation: Strategies include selecting resistant materials, applying protective coatings or linings, using corrosion inhibitors, implementing cathodic protection, and controlling the environment (drying, humidity control, pH adjustment). Proper design can reduce crevices and galvanic coupling, while regular maintenance and inspection help detect early damage.