Weathering Steel RFQ Checklist: Exposure, Drainage and Finish
A weathering-steel enquiry needs more than a rust-coloured reference photograph. Before comparing prices, establish what the component does, where it will be installed and which material and finish the project actually requires. A clear exposure brief helps the buyer, fabricator and designer avoid quoting different solutions under the same “Corten” description.
This checklist is for purchasing and coordination. It does not select a structural section, approve a facade system or establish a corrosion allowance. Those decisions remain with the responsible project designer.
1. Start with the service, not the appearance
Identify whether the enquiry concerns raw plate, formed sheet, a structural hollow section or finished metalwork. Record the specified grade and product standard separately. For example, ASTM A847 structural tubing and ASTM A606 Type 4 sheet and strip have different product scopes. Matching colour does not make them interchangeable.
Also separate outdoor atmospheric exposure from an industrial process. A tube inside heat-recovery equipment encounters the equipment's actual operating conditions. Outdoor patina guidance is not a basis for approving that service. For equipment versus structural tubing, use our separate A423 and A847 comparison.
2. Describe where moisture can remain
Weathering steel's protective surface develops under suitable alternating wet and dry exposure. Constant wetness or an enclosed damp face should not be treated as the same condition as an exposed surface that dries. SSAB's weathering-steel guide explains the role of this exposure cycle.
For an RFQ, attach a marked drawing or site photograph showing the installation position. Ask the designer to review the following conditions before the finish is finalized:
| Condition to describe | Useful information to include | Decision to resolve |
|---|---|---|
| Exposed face versus concealed face | Orientation, backing arrangement and access behind panels | How each face can drain and dry |
| Coastal air or de-icing spray | Actual site location and known salt exposure | Whether uncoated weathering steel is appropriate |
| Water-retaining or ground-contact zones | Contact areas, water level and proposed separation detail | Material and protection requirements for those zones |
| Hollow members and overlaps | End details, joints and inspection access | The designed strategy for excluding or releasing moisture |
| Adjacent finished surfaces | Paving, masonry, glazing or other finishes below the steel | Where drainage goes and how staining is managed |
Do not reduce suitability to one universal distance from the sea. The FHWA's technical advisory on uncoated weathering steel identifies local exposure, persistent wetness and detailing as relevant factors. It is highway-structure guidance, not an approval for every architectural or landscape product. A project-specific review is needed where conditions are uncertain.
3. Put run-off on the drawing
Water leaving the weathering surface can carry rust residue onto nearby materials. Mark the intended drainage route rather than assuming that a mature-looking surface makes staining impossible. SSAB's architectural recommendations address airflow behind panels and protecting surrounding finishes.
For a cladding enquiry, identify the panel's lower edge and the surface beneath it. For a planter or landscape feature, show the base interface and the intended outlet. Record who supplies any drainage or separation components. This turns an appearance concern into a defined part of the supply and installation scope.
4. Agree the delivery finish and the acceptance sample
State whether the quotation is for material that will weather naturally or for a separately agreed treatment. Describe which faces are visible, whether both faces matter and whether the sample is for colour, texture or workmanship. A photo without those details is a weak acceptance reference.
Ask the offer to name any included finish treatment and its maintenance instructions. Do not assume that “pre-weathered” means sealed, that a sealer is permanent, or that a sample guarantees identical outdoor ageing. If the project requires a treatment, its suitability and application scope should be resolved before order placement.
5. Send an enquiry that suppliers can compare
The following is a purchasing checklist, not a claim that every option is available. Unknown items can be marked “for project review” instead of replaced with assumptions.
- Product: plate, sheet, coil, tube or a named fabricated component.
- Material: complete grade, standard and edition required by the project.
- Geometry: dimensions, units, thickness or wall basis, quantities and drawing revision.
- Installation: site, intended function, exposed faces and identified moisture or salt conditions.
- Finish: delivery condition, visible faces, sample purpose and any specified treatment.
- Supply boundary: raw material or finished assembly; list fixings, supports and accessories separately.
- Acceptance: material documents, dimensional checks and agreed inspection requirements.
- Delivery: destination, unloading limits, packing and required arrival date.
When quotations arrive, compare these fields line by line. A lower price may cover a different material form, finish or assembly scope. Record departures explicitly and obtain the project's approval of substitutions before placing the order.
6. Plan access after installation
Unpainted does not mean that inspection can be omitted. FHWA's guidance emphasizes checking corrosion condition and keeping drainage and moisture-trapping deposits under control. The project should define appropriate inspection and maintenance for its particular design, including access to concealed areas. Do not promise a universal service life from the steel name alone.
Send a specification-led enquiry to ASC
Amardeep Steel Centre LLP is a supplier, exporter and stockist. Explore our weathering plates, sheets and coils or tube and pipe range, then send the required specification and the checklist details. The quotation confirms the offered product, dimensions, finish, documents and delivery scope.
Discuss your material requirement
This guide combines the linked producer and highway-authority guidance with a practical RFQ coordination checklist. It does not replace the applicable material standard, project design or specialist corrosion assessment.