Surface Finish of Galvalume Steel
| Normal（non-skinpassed）spangle | Skinpassed spangle | Regular spangle | Minimized spangle |
Weight of AI-Zn coating
The recommended nominal Al-Zn alloy coating weight is listed in the table below. Considering the use environment of galvalume steel sheet for construction purposes, the recommended minimum nominal coating weight is 50/50 g/m².
| Coating type | Recommended coating weight |
| Al-Zn alloy | 30/30,40/40,50/50,60/60, 75/75,90/90 |
| a: Coating mass 50g/m： equals to a coating thickness of 13.3pm approximately. | |
Surface Treatment of Galvalume Steel Sheet
| Item | Classification | Symbol |
| Coating type | Al-Zn alloy | AZ |
| Surface finish | Regular spangle | R |
| Minimized spangle | M | |
| Skin passed | S | |
| Surface treatment | Chromate passivated | c |
| Non-chromate passivated | C5 | |
| Chromate passivated + oiling | CO | |
| Non-chromate passivated+oiling | CO5 | |
| Anti-fingerprint | N | |
| Non-chromate anti-fingerprint | N5 | |
| Non-chromate high weather resistance anti-fingerprint | NW | |
| Oiling | 0 | |
| No treatment | U |
Aluzinc & Galvalume Steel Coil Coating Layer
- Anti-Finger printing ,Chromated, Oiled/ non-oiled
- Alu-Zinc Plating Layer
- Cold Rolled Steel Sheet
Aluzinc Steel Coil Process
Decoiling – Cleaning – Annealing – Zinc pot – Cooling – Air knife – Straightening – Post-treatment – Coiling
Detailed steps of the galvalume steel sheet processing
Step 1:
Pre-treatment: After the cold-rolled coil arrives in the galvalume workshop, after passing through the uncoiler, through the degreasing section and the reduction furnace, the steel coil is cleaned and its components are reduced to the extent that it can be galvanized.
Step 2:
Central section: The most critical technology is this step. After passing through the zinc pot, a layer of zinc layer is plated on the surface of the steel plate. After coming out of the zinc pot, it is cooled and shaped by the cooling tower.
Step 3:
Post-processing: The steel plate finally comes to the post-processing stage after various processes. After finishing, straightening and passivation, and finally coiling.
Galvalume Steel Coil Features
- Thermal Reflection:
People use it as material for heat-insulation for its thermal reflectivity as high as twice the galvanized steel sheet.
- Heat-resistance:
The aluzinc steel coil could bear above 300℃ high temperature with its good performance in heat-resistance, quite similar to the aluminized steel sheet’s performance in oxidation-resistance under high temperature. It is often used for chimney pipe, oven, illominator, and fluorescent lamp cover.
- Corrosive-resistance performance:
The essential of galvalume steel coil’s corrosive-resistance lies at aluminium’s protective property. Once the zinc come under abrasion, the aluminium would form a layer of densified oxidized aluminium, preventing the interior from further corrosion.
- Economical:
The density of 55%AL-Zn is smaller than Zn, therefore, with the same weight and thickness of coating, the galvalume steel sheet is 3% larger in area than that of galvanized steel sheet.
- Easily painted:
There is perfect adhesiveness between galvalume sheet and paint, saving the process of pre-treatment and weathering for painting work.
The coating material on the galvalume steel sheet is outstanding in its adhesiveness, which could be directly tarring on the advertising board and commonly used board with no pre-treatment such as weathering process.
- The galvalume steel sheet’s surface is luxury in silver colored appearance.
- Galvalume steel sheet and galvanized steel sheet are similar in performance of processability and painting.
Applications for Galvalume Steel Sheet
Construction: civil and industrial building roofs, facades, substrates for painted rolls, garage doors.
Industrial instruments: electric control cabinets, industrial freezers, vending machines.
Usually, building roofs are the most widely used.