Application of automated electrical resistance sensors for measurement of corrosion rate of copper, bronze and iron in model indoor atmospheres containing short-chain volatile carboxylic acids

• Formic and acetic acid accelerated corrosion of Cu and Cu–Sn from 300 ppb at 80% RH.
• Corrosion of Cu and Cu–Sn was barely affected by the acids at RH up to 60%.
• Iron corrosion activated at 1000–1590 ppb of formic acid in air at 80% RH.
• The ER technique has capacity to respond rapidly to changes in air corrosivity.

The corrosion rate of copper and bronze Cu-8 wt.%Sn increased rapidly when the concentration of formic or acetic acid in air reached about 300 ppb at 80% relative humidity (RH) and a temperature of 20 °C. It decreased slowly during the several days after pollutant removal due to the slow rate of pollutant desorption from the metal surfaces. Corrosion of these metals was barely affected by the acids at RH up to 60%. For iron, the critical concentration of formic acid in air which led to surface activation at 80% RH was between 1000 and 1590 ppb.