What Steel and What Coating? The Material Spec on a Panel Radiator — and How to Verify It

A steel panel radiator is, at heart, a pressed and welded steel box with a coat of paint on it. That sounds simple, and the finished products do look alike — same white face, same type numbers, same heat-output tables. But two radiators that read identically on a one-page datasheet can differ a great deal in the parts a buyer rarely sees: what steel they are pressed from, how thick that steel is, and what paint system protects it. As a family-run manufacturer exporting steel panel radiators to Europe, Russia, and Central Asia since 2002, we are asked about heat output and price far more often than about the material behind them — yet the material is what decides whether a radiator is still sound after fifteen heating seasons. This is a practical guide to the material specification: what to ask for, what proves it, and how a serious factory should respond.

The steel: cold-rolled low-carbon sheet, and why the grade and thickness matter Steel panel radiators are pressed from cold-rolled low-carbon steel sheet — the flat waterways and the convector fins are stamped and then seam-welded. The common European reference grades are the DC01-type low-carbon steels (EN 10130), chosen because they press cleanly and weld well. Two numbers decide how the radiator behaves under pressure and over time: the steel grade and the sheet thickness. Thickness is the one most worth pinning down in writing, because it is where cost is quietly saved. A typical panel uses waterway sheet around 1.2 mm and convector-fin sheet around 0.5 mm; shaving either figure lowers the material cost and, with it, the pressure margin and corrosion life. The relevant performance limits — working pressure and test pressure — come from the product standard and the [working and test pressure](/en/blog/radiator-working-and-test-pressure) your system requires, but they rest on the steel underneath, so the grade and the two sheet thicknesses belong in the order, not just in the brochure.

The coating: not one layer but a system The paint on a panel radiator is not decoration — it is the main corrosion defense on the outside of the steel, and it is a multi-step system, not a single coat. A typical factory process is: degrease and clean the pressed body, apply a phosphate or equivalent pretreatment so paint bonds to bare steel, apply a primer (commonly by cathodic electrodeposition, EPD/e-coat, which reaches inside the convector channels a sprayed coat cannot), then a powder topcoat that is oven-cured. What a buyer should verify is that all of these steps exist — a radiator that is simply powder-coated over bare steel, with no pretreatment and no e-coat primer, looks the same on day one and rusts from the edges and welds far sooner. Ask for the coating process in writing, and ask for the paint color reference (most export panels are a white close to RAL 9016). Internal protection is a separate matter from the paint: steel panel radiators rely on a correctly treated **closed** system for their inside surface, which is why [water quality and system care](/en/blog/protecting-steel-radiators-from-corrosion-water-quality) belong in the same conversation as the coating.

What actually proves the spec — and what does not A line on a datasheet is a claim, not proof. Three things move it closer to proof. First, the **material certificate (mill certificate, often EN 10204 type 2.1 or 3.1)** for the steel coil — this states the grade and, for a 3.1, the actual measured composition, and it ties the steel to a heat/batch number. Second, the **[Declaration of Performance (DoP)](/en/blog/reading-declaration-of-performance-steel-panel-radiators)** the manufacturer issues under EN 442, which declares the thermal and mechanical performance the construction is rated to — read alongside what [CE marking actually means](/en/blog/what-ce-marking-means-steel-panel-radiators). Third, the factory's own **production records and pressure-test log**: every panel should be pressure-tested, and a good factory can show the procedure. Note what a certificate does not do: an ISO 9001 certificate proves the factory runs a managed process, not that a given radiator is made of a given steel — that is [what ISO 9001 tells you and what it does not](/en/blog/is-iso-9001-a-product-certification-radiator-buyers). For material grade, you want the mill certificate; for performance, the DoP; for your specific order, the test records.

How to write the material spec into an order The cleanest way to protect yourself is to put the material into the purchase specification, not leave it to the brochure. A workable minimum: name the steel type (cold-rolled low-carbon, DC01-type / EN 10130) and the two sheet thicknesses (waterway and fin), state the coating system (pretreatment + e-coat primer + powder topcoat, with the color reference), state the required working and test pressure, and require the supporting documents — mill certificate for the coil, the DoP under EN 442, and the pressure-test record for the batch. On an [OEM or ODM order](/en/blog/oem-odm-custom-radiator-sourcing-china) this matters even more, because your brand name goes on a radiator whose material you specified. If you book a [third-party inspection](/en/blog/third-party-inspection-steel-panel-radiator-orders), these are the points the inspector verifies against the goods: thickness by gauge, coating by visual and film check, pressure test witnessed.

Ask the factory — and come and see the steel We would far rather a buyer ask about the steel and the coating than discover a gap after the first heating season. Send your specification to [lunan@jdradiator.com](mailto:lunan@jdradiator.com) / [kevin@jdradiator.com](mailto:kevin@jdradiator.com), call **+86-22-69189950**, or start at [www.jdradiator.com](https://www.jdradiator.com), and we will answer in material terms: the steel grade and thicknesses we press, our coating line step by step, the mill certificates and DoP we can provide, and how every panel is pressure-tested. Buyers who want to see the coil, the press line, and the paint line for themselves are welcome to arrange a factory visit in Tianjin — we have been a family-run radiator maker since 2002, and the material is easier to trust once you have seen where it comes from.