Surface treatment requirements for export steel structures should be clear before quotation. Coating damage, insufficient dry film thickness, poor curing, or unclear inspection records can create disputes after shipment and may delay site installation.
For EPC buyers, surface treatment is not only a workshop process. It affects corrosion protection, transport risk, owner approval, touch-up work at site, and the final quality document package.
1. Define the surface preparation grade
The RFQ should state the required surface preparation method and cleanliness grade. If this is missing, suppliers may quote different blasting levels or only light cleaning.
- Blasting grade or cleaning method required by the project specification.
- Surface profile requirement, if specified.
- Rust, oil, weld spatter, sharp edge, and contamination removal requirements.
- Whether edge grinding or corner rounding is required before coating.
2. State the paint system or galvanizing requirement
The coating system should be described by primer, intermediate coat, top coat, paint type, color, total dry film thickness, and expected exposure condition. For hot-dip galvanizing, define the applicable standard, coating thickness, venting/drainage requirements, and repair method.
| Requirement | What the buyer should specify |
|---|---|
| Paint system | Primer, intermediate coat, top coat, brand requirement if any, and color. |
| DFT | Minimum and total dry film thickness for each coat or full system. |
| Galvanizing | Standard, coating thickness, appearance requirement, and repair acceptance. |
| Touch-up | Factory repair method and site touch-up material recommendation. |
3. Control environmental conditions
Paint quality depends on workshop conditions. Ask the supplier how they record temperature, humidity, dew point, steel temperature, and ventilation during coating. These records are important when coating failures or curing problems appear later.
- Ambient temperature and relative humidity.
- Steel surface temperature and dew point margin.
- Maximum time between blasting and primer application.
- Curing time before handling, bundling, or loading.
4. Specify coating inspection records
Inspection records should show that each stage was checked before the next stage started. EPC buyers should request sample records before award and include the final record list in the RFQ.
| Record | Purpose |
|---|---|
| Surface preparation report | Confirms blasting or cleaning grade before painting. |
| Paint batch record | Connects coating material to the project package. |
| DFT report | Records dry film thickness by component, zone, or sample point. |
| Repair record | Shows damaged or thin areas were corrected before packing. |
5. Check coating before packing
Export packing can damage coating if steel components are bundled too early or without protection. Before packing, confirm that coating is cured, marks are readable, lifting points are protected, and steel-to-steel contact is controlled.
- Coating is cured enough for handling and bundling.
- Painted component marks remain visible.
- Padding, separators, or timber are used where needed.
- Small parts are packed to avoid coating damage and loss.
- Photos are taken before and after loading.
For delivery planning, use the export packing checklist and the component marking guide.
6. Clarify site touch-up responsibility
Some coating damage may happen during transport, unloading, or erection. The RFQ should state whether the supplier provides touch-up paint, repair instructions, or coating data sheets. The site team should know how to repair minor damage without using incompatible material.
7. Red flags during supplier review
- The quotation says "paint included" but does not define paint system or DFT.
- The supplier cannot provide a sample DFT report.
- Blasting and painting are subcontracted without record control.
- Components are packed before coating is cured.
- Loading photos show steel-to-steel contact without protection.
Buyer note
Surface treatment requirements should be priced and documented before award. A clear coating specification helps buyers compare quotations, reduce shipment damage, and prepare the quality file needed for project handover.