Steel Infrastructure Maintenance · Part 1 of 7
Assessing repair timing from corrosion condition and applying the G·SAVE system
The appropriate time to repair a hot-dip galvanized guardrail is better assessed from the condition of its remaining zinc coating than from installation age alone. Even structures installed in the same year can experience different rates of zinc consumption because of airborne sea salts, deicing salts, industrial atmospheres and time of wetness. Rails and fastening bolts may also develop different corrosion patterns because their initial coating thicknesses and local exposure conditions differ.
Maintenance decisions need to distinguish structural integrity from corrosion protection. A member and its connections may remain structurally sound while the protective function of the galvanized coating declines. Assessing and repairing the protective layer at this stage can address further corrosion while retaining the existing member. Where section loss or connection damage has developed, structural repair or replacement needs a separate assessment.
KEMP’s G·SAVE is an on-site repair system that forms a composite coating of zinc flakes and an inorganic binder on aged hot-dip galvanized surfaces. Its application begins with a condition survey and identification of the areas suitable for surface protection repair.
Zinc consumption depends on the exposure environment
A hot-dip galvanized coating protects steel both as a barrier and through the sacrificial action of zinc. Zinc corrosion products form during outdoor exposure, and the environment influences the condition and consumption rate of the protective layer.
On coastal sites, airborne salt deposition and repeated wetting and drying are important factors. Roadside assets also require consideration of deicing salts. Lap joints, fasteners and poorly drained areas that retain water and contaminants may corrode differently from freely exposed surfaces on the same structure.
Near industrial and chemical processing facilities, assessment should consider corrosive gases, dust and the composition of condensate. Direct chemical contact must be distinguished from atmospheric exposure: material compatibility depends on the chemical, its concentration and temperature. Even in inland environments, local condensation and standing water warrant separate inspection.
An installation age of 20 years therefore cannot, by itself, establish remaining coating life or the need for repair. Installation history and exposure conditions should be considered alongside coating thickness measurements and a corrosion survey. The corrosion protection life of the zinc coating is distinct from the structural service life of the asset. Reference: American Galvanizers Association.
Surface changes in rails and bolts help identify the repair window
The G·SAVE brochure illustrates corrosion progression through seven sets of photographs. It shows the loss of the initial metallic appearance, darkening and white corrosion products, followed by localized red rust and its spread. The brochure identifies a region described as 65–50% residual zinc as the preferred repair window.
The practical point is to intervene before red rust becomes widespread across the rail. Surface color and photographs cannot quantify residual zinc. Visual inspection helps select areas for investigation; remaining coating thickness and substrate condition are then checked to define the repair scope.
Red rust on fastening bolts is one inspection signal identified in the brochure. Using an example with 50 μm of zinc on the bolts and 77 μm on the rail, it describes rust appearing on bolts before spreading to the upper rail and larger surface areas. The brochure recommends repair of guardrails once red rust appears on their bolts.
Photographs from Yeoncho-myeon, Geoje, show upper-rail darkening in 2017, red rust on bolts and parts of the upper rail in 2019, and more extensive upper-rail red rust in 2021. They illustrate why component-specific surface observations should be recorded together with measurements, rather than grouping assets solely by age.
Figure 2. Bolt and rail corrosion examples from the G·SAVE brochure.
Figure 3. Photographs from Yeoncho-myeon, Geoje. Years and condition descriptions follow KEMP’s brochure.
Zinc content and binder weatherability need separate evaluation
The performance of a zinc-containing repair coating is not determined by zinc content alone. Zinc particle shape and connectivity, binder properties, adhesion to the substrate, film thickness and surface preparation all contribute.
The binders in organic zinc-rich paints can also degrade under outdoor exposure. Chalking under ultraviolet exposure is a familiar example for epoxy coatings. Chalking alone does not establish delamination. However, moisture and salts entering through coating defects or cracks can contribute to interfacial corrosion and loss of adhesion, potentially leading to lifting and peeling.
Zinc content therefore does not, by itself, establish long-term weatherability. Organic coatings should be assessed as complete coating systems, including appropriate topcoats and surface preparation. Repair material selection should consider binder stability outdoors alongside corrosion resistance. Reference: Carboline on atmospheric coating systems.
Figure 4. Existing coating failures shown in the Iksan presentation. Photographs alone do not establish the paint formulation or a single cause of failure.
The G·SAVE coating and its substrate requirements
G·SAVE combines overlapping zinc flakes with an inorganic binder. The layered particles extend the path that moisture and salts must travel through the film, while electrically connected zinc contributes to sacrificial protection. The inorganic binder is a component of the coating design intended to support outdoor weatherability.
Field work comprises condition assessment, cleaning and surface preparation, drying and inspection of the prepared surface, application, ambient drying and curing, and final inspection. Vehicle-mounted cleaning and coating equipment can be used along continuous guardrail runs. Connections, rear faces and other areas with restricted equipment access require a defined work scope.
Existing paint must be identified before specifying the work. G·SAVE is not applied over an existing paint layer. Painted application surfaces require complete removal of the existing paint, followed by assessment of the remaining galvanizing and steel substrate. The same requirement applies to organic paint films containing zinc.
Conventional maintenance painting can sometimes retain sound existing paint and repair only damaged areas. Such local repainting and a conversion to G·SAVE after complete paint removal have different preparation scopes. A conversion estimate must include stripping, waste handling and substrate preparation.
This gives the first corrosion protection repair of an unpainted galvanized member a practical process advantage. Cleaning and the required preparation remain necessary, but the repair specification can use the remaining galvanized surface without adding a full existing-paint removal stage. The first repair decision should therefore consider the work that a later change of coating system would require.
Figure 5. Surface preparation and application at Sunchang High School intersection. KEMP’s 2021 Iksan project presentation.
Field applications and performance evidence
Following its research and development work, KEMP carried out demonstrations over more than 10 km with multiple local governments and confirmed successful field application. Drawing on this installation experience, G·SAVE is commercially available for material supply and on-site work.
The construction new technology application documents include individual projects such as 600 m of guardrail rehabilitation at Hwajeon-ri, Ilgwang-eup, Gijang-gun, Busan, and approximately 2.2 km of surface restoration on Ulsan’s southern ring road. The project status records at that time listed completion and no reported defects for both sites.
After the Sunchang High School intersection demonstration documented in the 2021 Iksan Regional Construction and Management Administration project presentation, development work addressed spray uniformity, pressure stability, cleaning-liquid recovery and overspray collection. The second-year Ulsan field evaluation reported 1.1 km of coating restoration in one day. Production rates for a new site depend on access, the preparation required and working conditions.
External laboratory results are included in the revised final report for the transport research and development project. Key second-year specimen results were:
- Neutral salt spray: KS D 9502:2020, continuous exposure to 5% sodium chloride solution for 1,100 hours. The developed product was recorded as having no red-rust abnormality, while the conventional hot-dip galvanized comparison specimen showed red-rust abnormality. These findings apply to the client-specified conditions and assessment area, excluding specimen edges.
- Adhesion: class 0 in a 1 mm cross-cut test to KS M ISO 2409:2013.
- Pencil hardness: 8H to KS M ISO 15184:2012.
The field follow-up record, from application on December 16, 2022 to inspection on November 23, 2023, reported no peeling, defects harmful to use or additional corrosion over approximately 11 months.
The salt-spray result assesses corrosion resistance under the stated exposure. Cross-cut and pencil tests assess coating adhesion and surface hardness. These results do not directly establish years of outdoor service or guardrail crash performance; they are used with field observations to define an appropriate repair specification.
Figure 6. Before and after work at Sunchang High School intersection, in the Jeonju direction. KEMP’s 2021 Iksan presentation.
Figure 7. Field follow-up photographs from KEMP’s inspection record, approximately 11 months apart.
Compare costs using equivalent repair and replacement scopes
The economic value of on-site corrosion protection repair comes from retaining existing members and avoiding the associated replacement operations. New material, dismantling, transport and reinstallation costs are compared with preparation, coating and inspection costs.
For roadside guardrails with a 4.0 m span, the revised final report calculated a one-time restoration cost, including VAT, of 24.02% of replacement cost for the 2W type and 28.49% for the 3W type. These are repair-to-replacement cost ratios under the report’s assumptions. A current project estimate needs to reflect corrosion condition, existing paint, traffic management, access and quantities.
Sections requiring paint removal should be estimated separately from unpainted galvanized sections. Even when the repair material is the same, the surface preparation work can differ substantially.
Corrosion maintenance for steel structures that are difficult to dismantle
The Eiffel Tower in Paris has been maintained through repeated in-place surface preparation and repainting. Its operator describes a historical average repainting interval of approximately seven years. The tower is a painted puddle-iron structure, so its protection system differs from that of hot-dip galvanized steel. The shared principle is to maintain corrosion protection while retaining the structure in service. Source: the Eiffel Tower’s official maintenance account.
Replacing high-speed railway catenary masts or transmission tower members requires consideration of dismantling, lifting and reinstallation, alongside restrictions associated with rail operations or power supply. Where the structure remains suitable for repair, maintenance planning should assess residual corrosion protection and restore or supplement it to meet the exposure conditions.
Potential G·SAVE applications include hot-dip galvanized catenary masts, transmission tower members, lighting and sign supports, industrial supports and railings. Extending guardrail experience to another structure requires assessment of the existing finish, corrosion environment, remaining section and working conditions, followed by a structure-specific application and inspection specification.
A practical application review starts with photographs of the member and affected areas, its galvanizing and painting history, the exposure environment, coating thickness readings and the proposed quantity. KEMP uses this information to assess preparation requirements and an appropriate G·SAVE specification.
G·SAVE technical information · Discuss an application with KEMP
Part 2 will examine how corrosion management, structural inspection and protective coating repair contribute to infrastructure safety.
Sources and project acknowledgment
KEMP’s G·SAVE brochure; the Iksan project presentation; construction new technology application documents; and field installation and inspection records. The research evidence is drawn from the revised final report for project RS-2022-00144120, supported by Korea’s Ministry of Land, Infrastructure and Transport and the Korea Agency for Infrastructure Technology Advancement under the transport technology commercialization program.
General references: American Galvanizers Association — environment and coating life; Carboline — atmospheric coating systems; Eiffel Tower — repainting and maintenance.
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