Wind power
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.
Why hot-dip galvanizing was not an option
Tower sections in the 6–8 m diameter range have to leave the yard fully coated inside and out. The external face sees salt spray, UV and a splash zone that never fully dries; the internal face is a confined space where dehumidification is difficult and ventilation is limited. That makes the mix ratio and pot life of a two-component product the single biggest execution risk — with several crews working parallel sections, one wrong ratio leaves a patch that never cures, and that patch is inside a tower nobody will open for years.
System selection
Both faces take ZD96-1 as the base, single-component and ready to use straight from the container — that choice removes the mixing step entirely and with it the dominant failure mode above. External build: 80 µm zinc base, MIO epoxy intermediate, ZD6430 topcoat, 320 µm total. Internal build uses the same base at a lighter total, roughly 200 µm, finished with epoxy rather than polyurethane: there is no UV inside, so paying for an aliphatic topcoat would buy nothing.
How it was applied
Internal surfaces were sprayed with forced ventilation running, operators on supplied air and continuous gas monitoring — solvent-borne coatings in a confined space are an explosion and exposure risk, and this is the part of the job that governs the safety plan more than the coating does. Sections rotated on rollers so one set-up covers the full circumference. Flange faces, weld bevels and bolt holes were taped before spraying and the tape pulled while the film was still green; leaving it until cured tears the coating at the chamfer.
Acceptance and follow-up
External surfaces were checked to ISO 12944 for thickness and adhesion. Internal surfaces got an additional holiday test — low-voltage wet sponge on the epoxy finish, or spark testing where a conductive lining applies — because a pinhole on the inside of a tower is not visible again for the life of the structure. Flange mating faces must be free of coating; flatness is re-checked before the sections are bolted, since a film left on a mating face silently changes the preload.
Products used
Other projects
Transmission line lattice towers — field repair of galvanized steel
Galvanized lattice towers in a mountainous corridor had developed white rust and local red rust at bolt heads, weld seams and cut edges. Cold spray zinc was applied by brush and roller for in-place remediation without dismantling the towers or interrupting the line, restoring sacrificial protection at the damaged points.
Container handling cranes — repainting without removing the booms
Boom and girder sections too large for a galvanizing bath were blast cleaned in place and coated with cold spray zinc plus a metallic sealer. Work was phased around vessel calls, with two to three girder sections released per shift, so no crane was out of service for a full day.
Not sure which grade fits your environment?
Send us the structure, the steel condition and the corrosivity category (C2 to CX). We reply with a coating system, film builds and a delivered price.