TECHNICAL

Designing for Corrosion Protection

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

Many of the design requirements for good galvanizing will also ensure good drainage and optimum corrosion resistance. Fabricated assemblies should be designed to eliminate un-drained areas which will collect water and sediment in service, producing localised corrosion pockets.

The following rules should be followed:

  • Use butt welds in preference to lap welds
  • Where lap welds are used face joints downwards to avoid collection of moisture and sediment
  • Avoid use of horizontal boxed sections, ledges, seams and flat un-drained areas
  • Use rounded internal corners rather than squared corners in vessels and containers to avoid build-up of sediment
  • Design to eliminate crevices and unnecessary openings
  • Avoid contact of galvanized surfaces with brass or copper
  • Provide ventilation where possible in condensation areas
  • Under conditions of extreme humidity use an inhibitive jointing compound between contacting galvanized surfaces such as roof overlaps
  • Provide maintenance access where anticipated service life of certain components is less than that of the complete structure