Oil & gas
Tank farm — external shell and wind girder refurbishment
Twelve tanks in an inland refinery had coating breakdown at the shell course below the wind girder, where water collects. After surface preparation to Sa 2.5, cold spray zinc restored the base layer on the repaired bands; the remaining sound coating was feathered and overcoated, so only the failed bands were replaced rather than the full shell.
Why hot-dip galvanizing was not an option
Twelve tanks at an inland refinery, coating breaking down on the shell in a band under the wind girder. The girder creates a ledge where water stands, so that band stays wet far longer than the rest of the shell — long enough for a zinc-rich epoxy primer to blister and delaminate from the steel underneath. Replacing complete shell rings means emptying the tank, hot work and a long shutdown; a cosmetic topcoat repair, on the other hand, fails again within a year because the primer underneath is already gone.
System selection
The failed band only: blast to Sa 2.5 and rebuild the base with ZD96-1, chosen over zinc-rich epoxy because a sacrificial zinc layer keeps protecting the wet band even where the film is thin or slightly damaged, which is exactly the condition that caused the original failure. Then ZD6180 epoxy intermediate and ZD6430 polyurethane topcoat, 280 µm total. Sound areas around the band were feathered back at least 50 mm and coated directly, without stripping to substrate — that decision is what keeps the job at the cost of a band rather than the cost of a tank.
How it was applied
The tanks stayed in service — no emptying, no hot work — which dictated explosion-proof spray equipment, a classified work zone, and grounding and static discharge treated as the primary hazard rather than a formality. The angle between the wind girder and the shell is a dead corner for a spray gun, so it was built up by brush. Access was by suspended platform travelling around the circumference rather than full scaffolding, one band at a time.
Acceptance and follow-up
Pull-off adhesion at the transition between repaired band and sound coating — that interface is the weak point, since the new system has to bond to an aged film rather than to steel, and it is the first place a second failure would show. After completion, a visual and thickness survey of the whole shell before the tank went back into filling service, so any missed holiday would be found while the scaffold was still up.
Products used
Other projects
Cross-sea cable-stayed bridge — steel box girder and tower
Marine atmosphere at C5-M. Cold spray zinc was applied as the base layer on the steel box girder and tower segments that could not be sent to a galvanizing bath, then sealed and finished with an aliphatic polyurethane topcoat. Application was carried out in the fabrication yard on completed segments, avoiding post-assembly touch-up over the water.
Offshore wind towers — internal and external protection
Salt spray and constant humidity at the coast. Tower sections received cold spray zinc on the external surface followed by an epoxy intermediate and a polyurethane topcoat; the internal surface used the same base with a lighter build. The single-component format removed mixing errors across multiple application crews working in parallel.
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