Design for Maximum Corrosion Protection

Galvanized coatings provide outstanding corrosion protection for steel. Treatment of design details in accordance with good corrosion design practice as discussed below will further increase the life of galvanized steel fabrications.

Many of the design requirements for good galvanizing detailed earlier, such as the provision of flush-finished internal flanges in tanks and vessels will also ensure good drainage in service and optimum corrosion resistance.

Fabricated assemblies should be designed to eliminate undrained areas which will collect water and sediment in service, producing localised corrosion pockets.

The following rules should be followed:

1. Use butt welds in preference to lap welds.

2. Where lap welds are used face joints downwards to avoid collection of moisture and sediment.

3. Avoid use of horizontal boxed sections, ledges, seams and flat undrained areas.

4. Use rounded internal corners rather than squared corners in vessels and containers to avoid build up of sediment.

5. Design to eliminate crevices and unnecessary openings.

6. Avoid contact of galvanized surfaces with brass or copper as discussed under ‘What is Bimetallic corrosion?’.

7. Provide ventilation where possible in condensation areas.

8. Under conditions of extreme humidity use an inhibitive jointing compound between contacting galvanized surfaces such as roof overlaps.

9. Provide maintenance access where anticipated service life of certain components is less than that of the complete structure.