Forms of Corrosion in Seawater

The resistivity of freshwater is between 1000 and 3000 fi cm , depending on its salinity. The resistivity of seawater is only lOft cm . Seawater, therefore, facilitates ionic conductivity. However, for alloys commonly used for marine applications, the two most common forms of corrosion are pitting corrosion and galvanic corrosion. 

The most frequent form of corrosion is pitting corrosion, because the pH of seawater (8-8.5) is within the range in which aluminium and its alloys are prone to this form of 

Over the past 50 years, many results of immersion tests in seawater have been published [20, 21]. Table D.3.4 summarises the maximum pitting depths after 5 and 10 years 

AUoy Duration (ans) Total immersion I mmersion—emersion 

The effect of alternating immersion and emersion according to a tidal rhythm has no influence on the pitting depth, as shown by the results summarised in Table D.3.5. 

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