A laboratory study on metal corrosion by ammonia gas

The effects of aerial ammonia on metal corrosion was examined in this study . Tests were conducted using three environmentally controlled chambers at t hree different ammonia levels (0 ppm, 100 ppm, and 200 ppm). Four types of metal products (uncoated 1010 carbon steel, galvanized steel, Galvalume, an d pure zinc) were evaluated for weight losses and corrosion rates over a tw o-month test period. The test results showed that aerial ammonia, instead o f accelerating metal corrosion, reduced the corrosion rates for steel. Weig ht losses for uncoated 1010 carbon steel samples in the chamber without amm onia were three and six times higher than those in chambers with ammonia le vels of 100 ppm and 200 ppm, respectively. The corrosion rates were greatly reduced from 7.3 mu m/year to 1-2 mu m/year over the two-month period when ammonia level increased from 0 ppm to 200 ppm. For galvanized steel and pu re zinc samples, the influence of ammonia on the corrosion processes was no t apparent, however, there was a slight increase in corrosion rate for Galv alume samples with the increase of aerial ammonia concentrations.