Properties |
Galvalume Steel |
Galvanized Steel |
| Coating Process |
Hot dip coating process |
Hot dip coating process |
| Composition |
55% Aluminum, 43.4% Zinc & 1.6% silicon |
99.5% Zinc |
| Coating Glass |
AZ 150 Coating mass 150g/m2 (20m coating thickness on each side) |
Z275 Coating mass 275g/m2(19µm coating thickness on each side) |
| Density coating |
3.69 g/mcm2 |
7.11 g/m3 |
| Surface Area (size:0.38 (BMT)X 1220mm) |
Surface area is 261 meter/ tonne giving 5.0% more surface area than Z275 due to low density of alloy coating |
248.6 meter/ tone lower surface area due to higher density of Zinc coating |
| Type of protection towards Corrosion |
Barrier as well as sacrificial protection to steel. Hence it lasts for a longer period. The Zinc-aluminum coating retains the sacrificial properties of Zinc relative to steel and the aluminum oxide to increase barrier protection |
Zinc coating provides both barrier and sacrificial protection to steel |
| Metallic coating strength |
For Galvalume steel when strained, cracks occur within the coating but resist exposing the steel substrate until 12% uniaxial strain is reached |
For galvanized steel when strained cracks appear At the coating surface but resist exposing the steel substrate until 7% uniaxial strain is reached. |
| Surface protection |
Resin coated (1µm DFT Each side of strip) plus chemical passivation |
Chemicals passivation or oiling |
| Cut Edge protection |
The Zinc rich phase sacrificially protects the exposed edge and corrosion products fill the voids in the stable aluminum. This closes the contact of the corrosion attack to the steel base |
Zinc sacrificially protects the exposed edge of the steel Zinc coating will consumed entirely near cut edges far more quickly. One the Zinc coating sacrificial protection and rust unavoidably appears. |
| Sa pray (5% Nacl Solution) |
After 2000 hours only 25% of the area showed white rust and few tiny black spots were observed near the taped edges and spots were all edges unprotected: Zincalume steels samples last 9x longer than Galvanized All edges unprotected: Zincalume steel samples last 4x longer than galvanized. |
The white rust started within 24Hrs . After 500hrs.20% of the surface covered in red rust, rest is white rust and after 2000hrs, 95% of the surface is badly corroded |
| Chemical Resistance |
Excellent heat reflectivity, so less heat transmission. (Transmission on new material up to 654 watt/m2 out of 850 watt/m2 of solar radiation) |
Less Heat reflectivity, so more heat transmission. (transmission on new material up to 120 watt/m2 of solar radiation). |
| Temperature Resistance |
Resin coated Zincalume steel should not be heated above 150º C /300ºF due to degradation and fuming of acrylic resin coating. Non resin coated Zincalume steel recommended for service applications up to350ºC/600ºF, Above this alloying of Zn/Al coating and embitterment |
Suitable for continuous use up to 250ºC/480ºF, Above this there is Fe-Zn alloy growth and a tendency for zinc to diffuse into grain boundaries, resulting in embitterment |
| Lustre Property |
Spangles are small and tight, typically 1-2 mm and aesthetically looking good. Luster (brightness) lasts for a longer period of time |
Spangles are big and spangle boundaries are more prominent. |
| Lubrication |
Due to presence of resin coat (1um each side )on the surface, it acts as a lubricant and also resists scuffing and handling marks, thus no additional lubrication needed. |
Lubrication required during roll forming. |
| Paint Adhesion |
Excellent in pre and post painting |
Good |
| Corrosion Performance |
The corrosion performance pf Zincalume steel is at least 4 times better than galvanized steel. |
The Corrosion performance is poor compared to Zincalume steel. |
