Corrosion of Zinc Coatings in Indoor Environments
Indoor corrosion of zinc coatings is significantly milder than outdoor corrosion (typically reduced by approximately 80%) due to the absence of rainfall washout. The primary corrosion drivers indoors are elevated humidity levels or improper storage of damp products, leading to water condensation on zinc surfaces. Data indicates that corrosion activity peaks when relative humidity reaches 60% or 85-95%. Indoor corrosion incidents are most frequent in winter storage facilities.
Corrosion typically occurs beneath a thin electrolyte film containing dissolved oxygen. The corrosion rate is primarily governed by oxygen diffusion kinetics within the moist corrosion layer. Unlike outdoor environments, indoor corrosion products are not removed by rainfall but instead accumulate as porous, loosely structured deposits with increased volume and mass. These corrosion products exhibit strong alkalinity.
In kitchen environments, the presence of cooking fumes and combustion byproducts can triple the corrosion rate compared to standard indoor conditions.
Major indoor corrosion products include:
Zinc hydroxide [Zn(OH)₂]
Zinc carbonate [ZnCO₃]
