Stage 5. Galvanising
After lots of careful welding (we have to be sure not to distort or introduce too much stress into the structure) the whole chassis frame is hot dip galvanised. The frame is completely immersed in a bath of molten zinc. The chassis is designed to allow zinc to flow into and out of all sections, no matter what angle the chassis is at.
Unlike zinc plating, galvanising creates iron-zinc alloys at the surface of the steel, these gradually become pure zinc and then, after reacting with the air, layers of zinc oxide and zinc carbonate form. Even if all the zinc coatings wear away, the surface alloys are corrosion resistant (this is the shiny black you sometimes see on galvanised railings that are constantly grabbed by sweaty hands.)
Another benefit is that the process stress relieves the structure but this is where careful welding is important to minimise distortion.
Is it worth it? It's an expensive process but in over 20 years of galvanising Ibex chassis, we have never had a corrosion issue.