Galvanizing for Marine Environments
Galvanizing for Marine Environments
(OP)
It has been suggested to me that galvanized steel structures for a marine environment should be shot blasted before galvanizing.
I've not heard this before, has anyone any comments?
Peter
I've not heard this before, has anyone any comments?
Peter
RE: Galvanizing for Marine Environments
RE: Galvanizing for Marine Environments
A good property of HDG is that it has built-in quality control: the zinc simply does not adhere to surfaces that are not properly prepared and perfectly clean. So whatever surface you obtain with a HDG coating must have been prepared well enough.
Of course, if you are applying a zinc-rich coating (paint) then thorough cleaning and profiling the surface with an abrasive blasting process (abrasive choices are many) is recommended, especially for inorganic zinc.
RE: Galvanizing for Marine Environments
As Rustbuster has already pointed out HDG normally involves a series of de-greasing, acid pickling, fluxing etc. before dipping in molten zinc.
It is my understanding, that if the steel is shot blasted before entering the HDG process, the final thickness of zinc coating taken up by the steel can be increased by almost 50%. The normal HDG process only adds a finite thickness of zinc regardless of the amount of time in the bath. Any method of increasing this coating uptake is bound to increase the long term protection of your steel.
Regards
Mike
RE: Galvanizing for Marine Environments
One caution -- the coating sacrifices over time (what life do you need) but this is only meaningful in normal Ph ranges. Strongly acid or alkaline environments remove galvanizing at astounding rates, and extra thickness might buy you only weeks of protection. On the other hand, just being in straight sea water with low salt can be overrated. I have seen bare steel with 1/8" all round cushion last for decades.
Finally, will you have to field to weld? Can you paint and especially patch? Can you inspect and maintain the end product? Best to treat this as a system, and then integrate your blasting if it still makes sense.