The effect of selected amines on the corrosion of carbon steel and copper was investigated in the laboratory and in the field. The steel and copper samples were exposed to loads of the amines in the laboratory, representing estimated 10 years worst case exposure due to emission from a CO2 capturing plant at the Technology Centre Mongstad (TCM). No effect on the corrosion rate for steel was detected for this dose as compared to blanks. Application of 700 times higher doses of amines in the laboratory was observed to give anodic protection, and thus reduced corrosion, of steel samples, but to dissolve the surface of a copper sample. The anodic protection was due to the formation of an amine surface film that protected the sample from oxidation. The dissolution of copper was probably due to formation of a copper - amine complex at high pH. A slight increase in corrosion was observed for samples that were exposed to the equivalent of 65 years worst case exposure of amines in the field. This may be explained by freezing point depression and increased time of sample surface wetness due to accumulation of the amine solute on the surfaces during the frost season.
This report describes the work and results from a study of the possible effect of amine deposition on corrosion of steel and copper. The work was performed as a part of the project:
Amine Emissions during Carbon Capture. Phase II: Experimental Study Investigating Risks of selected Amines (ExSIRA)
Solutions in water of the amines: MEA (Monoethanolamin), DEA (Diethanolamin) and AMP (2-amino-2-methyl-1-propanol), were applied to steel and copper plates of dimensions 15*10*0.1 cm in controlled climate conditions in the laboratory at NILU - Norwegian Institute for Air Research, and positioned for one year outdoor in a field test in the locations of Skøyen-Oslo, Borregaard, Birkenes and Tanananger in Norway, representing an urban background, industrial, rural and coastal station, respectively.
The concentrations of the applied amine solutions were determined based on modelling of the maximum expected deposition of amines due to amine emissions, according to the “design” scenario, from an Aker Clean Carbon (ACC) technology CO2 capture plant using flue gas from the CHP (Combined Heat and Power plant) (Berglen et al. 2010, pages 26-29). Maximum or higher than maximum doses of amines expected to deposit from the CO2 capture plant were used. To simulate a more aggressive atmosphere some samples were exposed to SO2 in the laboratory in addition to the exposure to the amines.
The corrosion of the samples was documented by optical photography of the samples after exposure. The corrosion was determined by the weight loss of the samples after chemical stripping and the elemental composition of the samples was determined by x-ray analysis in a scanning electron microscope (SEM-EDX). The ISO corrosion category for the locations was determined from the measured annual corrosion.
Monthly average values for the amount of the pollutants that are known to affect carbon steel corrosion was measured at the exposure locations in the field by passive sampling of SO2 and aerosols which were analysed for their content of ions. Approximate values for the annual average temperature and precipitation at the experimental stations were obtained from the nearest climate stations with available data in eKlima (2012), which were located less than 10 km away from experimental field stations.
The effect of the amines on the corrosion was analysed by comparing the corrosion weight gain, or weight loss of the samples after stripping of the corrosion layer, and elemental content of the corrosion layer, for samples to which an aqueous amine solution or only water had been applied.
The effect of the environment on the corrosion was analysed by single correlation of the measured annual corrosion at the stations with the measured pollutants or climate factors.