Chromate Free UV Stable Color Coated Steel Coil Anti Chalking Finish

Chromate Free UV Stable Color Coated Steel Coil Anti Chalking Finish

Chromium based passivation has protected galvanized surfaces for decades, but it conflicts with restricted substance rules in many export markets. This coil replaces it with a chromium free conversion coating, then builds a UV stable anti chalking polyester system on top. The result is a prepainted galvanized coil that can be documented as RoHS compliant without asking the customer to accept an exemption.

Removing chromate is not simply a substitution. The chromium free layer needs tighter process control on bath concentration and dwell time, otherwise adhesion drops after humidity exposure. We verify the change with a 24 hour water soak and a cross hatch test on every production run.

Parameters

Advantages

• Documented RoHS compliance without exemption notes attached to the project file.
• Anti chalking top coat keeps exterior surfaces from whitening under long sun exposure.
• Adhesion verified after water soak, which is where chromate free systems usually fail.
• Works with standard roll forming, bending and profiling equipment.
• Available with matched back coat for two sided panel assemblies.

Where It Fits

• Building products exported to the European Union
• Consumer facing structures with restricted substance policies
• Roof and wall panels for green building certification projects
• Electrical enclosures and equipment housings

Frequently Asked Questions

Is chromate free coating less durable?

Not when the process is controlled. The main risk is adhesion loss under humidity, which is why every batch is water soaked and cross hatch tested. In salt spray the difference against conventional chromate is small at 500 hours.

Can you provide compliance documents?

Yes. We issue a RoHS declaration with the shipment and can add a third party test report for restricted substances when the project requires independent verification.

Does the UV stable top coat change the color?

The stabilizer package is transparent, so the color reading stays within the usual dE 1.0 window. Very light shades may shift slightly warmer because the chromium free pre treatment is less blue than chromate.

What is the minimum order?

Five metric tons for standard colors and gauges. For colors outside our stocked RAL list the minimum rises because the coating line needs a dedicated run.

Packing and Documentation

Each coil is wrapped in PVC film with paper interleaving, strapped on a wooden pallet and labelled with heat number, coating batch and film thickness. The shipment pack includes the mill certificate, the chromium free process declaration and the RoHS statement. For projects that require it we arrange third party laboratory testing of restricted substances before dispatch, so the documents arrive with the coils rather than weeks later when the panel line is already running. Documents are issued per shipment, not per order, so split deliveries stay traceable.

Coating thickness matters more than coating brand in service: Top 20 - 25 micron, primer 5 micron. Below roughly 20 micron total build, UV exposure in strong sun starts to chalk the surface within a few years, and the colour drifts before the steel itself shows any problem.

Formability is specified as T bend 2T without cracking. This determines whether the strip can be roll formed and folded at the job site without cracking the coating over the bend radius, which is the most common cause of premature coating failure on roofing panels.