Avances en la medida de la protección catódica de estructuras metálicas enterradas mediante métodos de desconexión cíclica

Resum

This PhD Thesis Memory discusses five field assessments of the cathodic protection (CP) of coated steel pipelines buried in soils of an average resistivity of 4300 Ω cm, performed using the close interval survey (CIS) technique and incorporating the instant-off potential (IOP) method to measure any voltage drop. Multiple current sources were identified in the surveys and simultaneous interruption of all the current sources was achieved by use of synchronised switches. The results presented here highlight the importance of incorporating the IOP method when performing CIS in order to quantify the voltage drop factor and thus improve the interpretation of potential measurements. Unexpected field situations encountered when performing the CIS technique are discussed and the practicality of using corrosion coupons is analysed. The cathodic protection (CP) of on-grade coated steel storage tanks deployed on reinforced concrete slabs in soils of 20-30 kΩ cm resistivity was evaluated for two different time periods nine years apart. The required CP current was calculated and the ohmic drop was measured using the instant-off potential (IOP) method. The resulting polarisation shift is a useful indicator of the level of protection afforded and whether the potential criterion or the polarisation shift criterion is fulfilled. It was also noted that the greater the ground resistivity, the less corrosive the environment for an on-grade steel structure.