CORROSION OF STEELS IN POTABLE GROUNDWATER .2. EXPERIMENTAL-ANALYSIS

We have found that some bacteria able to induce metallic corrosion wer e present in water cells used by heat pumps. After the appearence of d ifferent problems encountered on these installations, we have decided to study the behaviour of steels commonly used for casing. To reproduc e short and long term corrosion. we have followed these materials duri ng 18 months with different analyses at 3, 8 weeks and at 12 and 18 mo nths. The two stainless steels (AISI 304L and 430) have similar behavi our. On the other hand, the low carbon steel (NF E24) and the low allo yed steel (APS20A) present important similarities. DC and AC analysis show that E24 and APS20A have a complex behaviour. But both can be sim ulated by elementary electrical analogues as a one time constant circu it in the early stage and by a two nested time constant circuit after 18 months with a diffusional process (Warburg). SEM observations and X -ray diffraction spectra have given important informations on the chem istry and the geometry of the surface (bacteria, crystals...).