ACET : a fast tool for anticorrosive properties assessment. The offshore wind power case

ACET (Accelerated Cyclic Electrochemical Technique), nowadays standardized under UNE 48315 and shortly under ISO 17463, is one of the fastest tool for assessing the anticorrosive properties of organic and inorganic coating systems ; 24h are enough for obtaining quantitative results. Several years of work allowed good correlations with the salt fog spray and better understanding of the failure mode. Nevertheless, combined cycles for anticorrosive properties assessment seems to correlate better the natural exposure.

The protection of the sea wind turbines involves three areas with different corrosivity conditions : the atmospheric zone that does not come in contact with the sea water ; the splash zone that comes into contact with the waves breaking against the turbines ; and the submerged zone below sea level. The standard ISO 12944-2, which provides different corrosivity categories, includes the atmospheric zone in the category C5M-High durability. The requirements for the manufacturers of coating systems used in the protection of the off shore structures are based on the standard ISO 20340. This regulation requires the specimens to be tested as follows for 25 one-week cycles : neutral salt spray environment (3 days) ; QUVB exposure (3 days) ; temperature of -20oC (1 day). The assessment is then carried out by carving the specimens and measuring the penetration of corrosion (in millimetres) in new spots, thus obtaining the average value and the standard deviation.

In this communication we present the correlation between the electrochemical information given by the ACET and the results obtained after exposure to the combined cycle of the ISO 20340 test. In little more than 24 hours – the time needed for the test and the subsequent data processing –it is possible to obtain estimates of the penetration within the tolerances of the values obtained by the traditional technique at the end of 25 cycles. This innovation is in line with the need to generate renewable energies by using ecologically and economically efficient generators.