HD Galvanized steel vs Aluminum 5052 H32, Resistance to salt Spray Test

A. Salt spray testing is inappropriate for hot dip galvanized steel, and any comparison using that test will give misleading results.
The mechanism that HDG affords corrosion protection is through the oxide and carbonate layers that form on the surface of the zinc coating. These are highly weather resistant, but not resistant to the type of action that salt spray cabinets give. In fact the cabinet action will remove the protective layer, accelerating the erosion, and the removal of zinc appearing to give a short life. If that data is then used to predict real-world performance, grossly inaccurate results will ensue.
Salt spray does not predict life expectancy for HDG.

Hi Santhosh. Although Geoff notes that salt spray testing is inappropriate for galvanizing, it should be okay for powder coated GI. And I'll bet that it significantly outperforms conversion coated aluminum in salt spray testing because properly applied organic coatings like powder coating almost always outperform metal based coatings in salt spray testing.

But the issue is still fraught with issues, such as the pass/fail criteria for salt spray testing being different for powder coated steel than conversion coated aluminum :-)

Regards,