Atmospheric corrosivity map for steel in Canary Isles: Fid-Bau Portal

Atmospheric corrosivity map for steel in Canary Isles

Santana, J.J. / Santana, J. / Gonzalez, J.E. / De La Fuente, D. / Chico, B. / Morcillo, M.

On small islands like the Canary Isles the atmospheric corrosion of metals is a major concern, especially for the electricity and building industries. corrosivity maps provide a helpful tool for selecting suitable materials, protection systems, maintenance intervals, etc. In the work an atmospheric corrosivity map for steel has been developed in the eastern zone of the Canary Isles archipelago following ISO standard 9223. The proposed map is based on corrosion rate results measured at 39 test sites located across the zones three main islands: Gran Canaria, Fuerteventura, and Lanzarote. Corrosion in Canary Isles is highly dependent on atmospheric salinity. Salinity depends mainly on the condition of exposure to the wind regime (trade winds) and on the distance from the coast. The damage functions obtained confirm the great dependence between salinity and the corrosion values obtained. With regard to atmospheric corrosivity, 3 zones can be distinguished for each of the islands: (1) high or very high corrosivity (categories C4 and C5); up to 500 m from the shoreline and on the coastline most exposed to marine aerosol (northern and eastern coasts), owing to the characteristic northeasterly direction of the trade winds. The corrosion rates found are between 52.7 and 233 micron/year. (2) medium corrosivity (category C3); including some coastal zones (southeast) and a strip of land between 500 m and 3-4 km from the shoreline in the coastal zone most exposed to aerosol. Corrosion rates between 25 and 50 micron/year are found. (3) low corrosivity (category C2); including the atmospheres of the central areas of the islands and part of the coastline of the three islands least exposed to the aerosol (west) with corrosion rate values of less than 25 micron/year but in all cases higher then 11 micron/year, which is the lowest value found.