Published · 2026-10-08
A coating figure is useful only when its meaning is clear. Before comparing a roof sheet, panel face or purlin offer, separate the steel substrate, metallic coating and any colour-paint system. Record the measurement unit and the surfaces covered by each stated value. A higher number in a different unit is not a reason to accept an offer as equivalent.
Read the manufacturer's unit definitions
Tata Steel's metallic-coated page separates double-sided coating mass in g/m² from coating thickness per side in µm. Keep those definitions with the values. [1]
BlueScope's ZINC HI-TEN page uses Z275 as a coating-mass designation and qualifies coating options by steel grade. Confirm the exact offered combination. [2]
These are manufacturer examples, not ZY supply specifications. Neither a coating label nor this guide establishes the applicable project standard, corrosion lifetime, warranty or availability. Obtain documentation for the material actually offered.
Put six separate items into the comparison
| Item | What to record or ask |
|---|---|
| Steel substrate | Grade, sheet thickness definition and the corresponding drawing or schedule. Use the BMT/TCT guide for that separate thickness question. |
| Metallic coating | Coating system, designation and applicable standard and edition; keep these separate from the steel grade. |
| Coating mass | Stated value, unit, whether it covers one side or both sides, and the supplier's referenced requirement or record. |
| Coating thickness | Unit, measured layer, side and measurement basis. Do not turn a mass figure into thickness without the applicable method and assumptions. |
| Colour-paint system | Top and back finish requirements, layer descriptions and any specified documentation; do not treat paint as the metallic coating. |
| Material evidence | Offered material identification, inspection documents, stated acceptance basis and the person responsible for resolving differences. |
Resolve the unit gap before the price gap
Illustrative comparison, not a customer case: Offer A states coating mass for both sides. Offer B states coating thickness per side. First ask each supplier to complete the same coating fields and identify the applicable documents. Keep unresolved entries open. The two descriptions alone do not establish matching materials, and an omitted entry does not by itself prove a defect.
Offer A · Coating mass
- Unit stated
- g/m²
- Side definition
- Both sides
- Clarify before comparing
- Coating system, applicable specification, acceptance basis and material record.
Offer B · Coating thickness
- Unit stated
- µm
- Side definition
- Per side
- Clarify before comparing
- Measured layer, side, measurement basis and material record.
Keep exposure and approval responsibilities explicit
Tell the responsible project designer where the material will be used and which exposure, cleaning, cut-edge or interface requirements need review. Ask the supplier to identify the offered coating and the relevant instructions. Record the approving party, unresolved questions and response dates. Avoid adding a service-life promise or a cross-system equivalence to a quotation comparison without supporting evidence.
Prepare a coating-description enquiry
Fill in known information and leave unresolved fields marked for confirmation. This worksheet supports procurement; it is not a coating test report, design approval or corrosion assessment.
- Project reference and destination
- Product, drawing or member schedule reference
- Steel grade and sheet thickness definition
- Metallic coating system and designation
- Applicable coating standard and edition to confirm
- Coating mass, unit and one-side/both-side definition
- Coating thickness, unit, layer and side if stated
- Top and back colour-paint requirements if applicable
- Material identification and requested inspection documents
- Exposure, interfaces and responsible reviewing party
- Quantity, supply boundaries and unresolved questions
Connect the material description to the product schedule
Primary sources and scope
Sources checked on 8 October 2026. The publication dates of the manufacturer source pages were not established. This is a procurement guide, not a report of a new event.