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Corrosion Zone Categorisation and First year Mild Steel Corrosion Rate (g/m²)

Corrosion Zone Categorisation and First year Mild Steel Corrosion Rate (g/m²)

NZS3604Code of PracticeDescriptionMS Corrosion Rate (g/m²)
BA  (Mild)Far inland, with no industrial pollution or thermal activity, or dry internal. This condition is not commonly found externally in New Zealand.1 – 10
B  (Moderate Inland)Most dry rural areas in New Zealand, 50 km from the coast, are in this category. It can extend closer to the coastline of sheltered water in low rainfall areas.10 – 80
CC  (Moderate Marine)This category covers area of low marine influence. It can extend from 50 km inland to within 1 – 1.5 km of west coast beaches, or be in the immediate vicinity of calm estuaries.80 – 200
DD  (Severe Marine)In this category, marine influences are frequently apparent. Its proximity to the coast is determined by the roughness of the water, prevailing winds, ground roughness and sheltering.200 – 400
E  (Very Severe Marine)In this category, the structure is normally exposed and marine influences are almost constantly apparent.400 – 650
F  (Extreme Marine)This category is rare in a building site. It would be an exposed location very close to breaking surf.650 – 1 000
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