Repeat repairs to galvanized structures incur costs for rust removal, recoating labor, access equipment, transport and work-zone control, in addition to coating materials. Cost-effective specification starts with selecting a coating system for the condition of the remaining zinc layer and distinguishing factory treatment before dispatch from application on site.
GSAVE is a repair coating that forms a protective zinc-flake layer. GPLUS is a transparent inorganic post-treatment that inhibits oxidation and dissolution of zinc-based surfaces. Distinguishing corrosion-protection restoration on deteriorated galvanized surfaces, supplementary protection of existing components and corrosion-resistance enhancement of new products provides the basis for selecting the coating and application process.
Select the coating system by surface condition and required function
| Target surface | Required function | Application |
|---|---|---|
| Corroded hot-dip galvanized surfaces or exposed steel substrate | Restore the protective zinc layer | GSAVE after rust removal and surface preparation |
| Existing components and fastened joints with a remaining zinc-based protective layer | Enhance the corrosion resistance of the remaining layer | GPLUS after surface preparation |
| New zinc-electroplated or hot-dip galvanized members and fasteners | Enhance corrosion resistance before dispatch | GPLUS post-treatment after zinc coating |
Site assessment covers remaining zinc thickness (μm), the area affected by red rust (m²), exposed steel and adhesion of the existing coating. Where steel section loss has occurred, structural integrity is assessed first. Before applying GSAVE to a surface with an existing organic coating, that coating is removed to expose the galvanized surface or steel substrate.
GSAVE: barrier protection combined with sacrificial anodic action
The plate-like zinc particles in GSAVE form an overlapping structure that obstructs the ingress of moisture, salts and other corrosive agents. At exposed steel, zinc provides electrochemical protection through sacrificial anodic action. Applications include deteriorated hot-dip galvanized structures, damaged galvanized areas, cut edges and welds.
The repair sequence is rust removal and degreasing → substrate preparation → GSAVE application → ambient-temperature curing → coating inspection. GSAVE also applies where part of the galvanized layer remains but corrosion has progressed to the point that restoration of corrosion protection is required. Dry film thickness (DFT), number of coats and curing conditions are controlled according to the formulation and application specification.
SST durations for standard and aerosol formulations
| Product and substrate configuration | SST duration |
|---|---|
| GSAVE standard formulation over hot-dip galvanizing | 3,000 h |
| GSAVE standard formulation on steel | 1,500 h |
| GSAVE aerosol over hot-dip galvanizing | 1,500 h |
| GSAVE aerosol on steel | 1,000 h |
Specimens coated with the standard GSAVE formulation over hot-dip galvanizing underwent salt spray testing to ASTM B117, with 5% NaCl at 35°C. After 3,000 hours, a small amount of white rust was observed, with no red rust or coating peeling. This result applies to the tested system comprising hot-dip galvanizing and a GSAVE topcoat.
40 cyclic corrosion test cycles on coated steel panels
GSAVE-coated steel panels remained free of red and white rust after 40 cyclic corrosion test (CCT) cycles under JIS H 8502:1999. Each cycle comprised the following four stages.
| Stage | Conditions and duration |
|---|---|
| Salt spray | 5 h |
| Drying | 70°C · 2 h |
| Humidity exposure | 50°C · 90% relative humidity · 3 h |
| Drying | 60°C · 2 h |
12 hours per cycle × 40 cycles = 480 hours of total exposure to repeated salt spray, drying and humidity stages. This evaluates coating performance under cyclic environmental exposure, separately from continuous salt spray testing (SST).
GPLUS: enhanced corrosion resistance for new and existing zinc-based surfaces
GPLUS is a transparent inorganic coating for zinc-plated, zinc-alloy-plated and zinc-based coated surfaces. It improves corrosion resistance by inhibiting zinc oxidation and dissolution and restricting the ingress of corrosive agents. It serves as a post-treatment for members and fasteners where the original appearance of the zinc coating is to be retained.
New-product post-treatment: 1,500-hour SST on hot-dip galvanized pipe
GPLUS post-treatment of newly zinc-electroplated or hot-dip galvanized products provides additional corrosion resistance before dispatch. Spray, dip-spin or roller application is selected according to component geometry and production volume. Key objectives include suppressing white rust and improving corrosion resistance in zinc-coated fasteners and members intended for coastal or chemical-industry environments.
After 1,500 hours of ASTM B117 salt spray testing, the GPLUS-treated and untreated hot-dip galvanized pipe surfaces show different corrosion progression. The left side received GPLUS post-treatment; the right side has hot-dip galvanizing alone. When assessing additional protection for new products, treated and untreated surfaces are compared within the same test.
Protection after mechanical damage: 480-hour SST following 2 tightening cycles
Zinc-electroplated, hot-dip galvanized and zinc-flake-coated (ZFC) bolts and nuts underwent 2 tightening cycles. GPLUS aerosol-treated and untreated groups were then compared through 480 hours of ASTM B117 salt spray testing. The treated group showed suppression of corrosion progression.
This test evaluates enhancement of corrosion resistance in zinc-based protective layers mechanically damaged during assembly. Where steel is exposed and the protective layer needs to be re-established, rust removal, surface preparation and GSAVE repair are performed first. A GPLUS topcoat is then applied where required by the supplementary protection specification.
Technical and economic assessment by area, labor and equipment input
Direct costs for on-site repair extend beyond the unit price of the coating. For the same work scope, material consumption, preparation and application labor, and equipment operating days should be calculated separately.
C₀ = A × cₘ + H × cₕ + D × cₑ + Canc
| Variables and units | Cost basis |
|---|---|
| A · cₘ m² · KRW/m² | Application area · material cost per unit area |
| H · cₕ person-hours · KRW/person-hour | Preparation, application and inspection labor · labor rate |
| D · cₑ equipment-unit-days · KRW/equipment-unit-day | Equipment input · equipment rate |
| Canc KRW | Separate costs such as transport, work-zone control, removal and reinstallation |
GSAVE: on-site repair that reduces the scope of removal, transport and reinstallation
Members that retain structural integrity and are suitable for on-site repair can have their corrosion protection restored in place. Compared with replacement or factory reprocessing, removal, transport and reinstallation costs are major cost-difference items. GSAVE application costs include rust removal, degreasing, removal of existing coatings where necessary, application and inspection labor. Ambient-temperature curing allows the work to be organized without separate heat-curing equipment.
For localized damage, calculate the actual repair area A and the scope of edge preparation. For widespread deterioration, assess the total application area and surface-preparation productivity. Damage distribution and working height affect H and D even on the same structure, so both KRW/m² and total application cost should be compared.
GPLUS: the cost structure of field protection and factory post-treatment
On existing galvanized components, incorporating GPLUS application into scheduled inspection, assembly or maintenance can reduce duplicate site visits and equipment mobilization. Quotations should distinguish labor already included in the planned work from the additional labor required for application, curing and inspection.
For new products, post-treatment cost per component = total batch material, labor, equipment and inspection costs ÷ number of accepted components. Compare alternatives for the same component, volume and required corrosion resistance, and assess the access-equipment and work-zone-control costs of repairs after installation separately. Factory post-treatment provides the process advantage of protecting surfaces before dispatch that will be difficult to access after installation.
If repeat repairs are required, cumulative direct cost = initial application cost C₀ + the sum of direct costs for each subsequent repair. Each repair includes the required coating removal, repeat surface preparation, recoating and site remobilization. Defining the GSAVE repair scope and timing of GPLUS post-treatment in advance aims to reduce unnecessary repetition of work and site mobilization.
Specify the application process for the component and zinc coating
Send component photographs, the existing zinc-coating and coating-system specifications, the service environment, and application area (m²) or quantity (units) to request an application assessment from KEMP. For deteriorated structures, the assessment considers the remaining zinc layer and surface-preparation scope. For new products, it considers the required corrosion resistance and production process. These define the GSAVE or GPLUS application scope and the basis for cost estimation.
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