Galfan® (ZA) coatings are produced when a steel coil continuously runs through a hot-dip bath of 95% zinc and 5% aluminum. Compared to traditional zinc (GI) coatings, zinc-aluminum coatings have both superior forming properties and corrosion resistance.
Zinc-aluminium coated steel has about twice the corrosion resistance of hot-dip galvanized (GI) steel. “Galfan” is the coating’s registered trademark and the EN 10346 standard refers to “ZA.” But many manufacturers call this coating “zinc-aluminum” or ZA, while ASTM uses the “GF” designation.
Galfan coatings can be used to achieve a longer service life for a steel part, or to replace traditional zinc coatings with a thinner ZA coating – thereby simultaneously offering improved weldability and formability properties. The eutectic composition of 95% Zn and 5% Al improves coating adhesion and enables a lamellar coating microstructure, which makes Galfan coatings ductile and well-suited for deep drawing.
Because Galfan coating is sacrificial, it can still provide a level of corrosion resistance to cut edges or surfaces where the ZA coating has been damaged: scratches, impacts, etc. ZA’s low peeling tendency – due to its low-friction and tight bond to the steel substrate – provides uniform corrosion resistance, even on heavily formed steel parts.
SSAB offers Galfan coatings with different coating thicknesses, surface qualities and surface treatments to meet the demands of various applications.
* In triple spot test
In addition to these EN10346:2015-defined Galfan coating thicknesses, we also offer: asymmetric coatings; symmetrical coatings with a minimum mass per surface and other coating techniques to OEM specifications: please contact us for details.
Compared to traditional pure zinc coatings, zinc-aluminum coated steel provides superior formability, making it well suited for deep drawing, roll forming, profiling, and bending. ZA-coated parts also have great resistance to cracking, delamination, and powdering due to the thin intermetallic layer at the substrate and coating interface. This is why ZA coatings are highly recommended for steel parts with demanding forming operations.
When forming Galfan coated steel, you may need to make changes to, for example, tooling lubrication, tooling geometry, and holding forces. Additional considerations include the thickness of the ZA coating, surface quality and protection.
ZA-coatings also have the advantage of acting like a lubricant, making them ideal for forming that uses low-to-moderate surface pressures. Galfan coating’s lamellar microstructure is extremely well suited to roll forming, demanding deep drawing, profiling, and bending.
Many adhesives used for zinc-coated steels can also be used for zinc-aluminum coated steels.
For mechanical joining of ZA-coated steel, bolts, rivet tabs, and non-tabs methods can be used. Lock-seaming, folding, tab and compression joints are all suitable for Galfan coated steels, due to ZA’s superior formability. Flame or arc soldering can also be used for ZA-coated steels.
Galfan coated steels can typically be welded using resistance, laser, and arc welders, achieving welded joints with mechanical properties equal to those of non-coated steels.
ZA-coated steel can be welded using the same parameters as for zinc (Z) coated steel. If the coating thickness is reduced by using zinc aluminium coatings, the required welding current and electrode force can be lowered, extending the service life of welding electrodes.
Note that all zinc-based coatings produce zinc oxide welding fumes, requiring proper ventilation of the work area.
In addition to providing the desired color for the final product, painting further improves the corrosion resistance of the steel part.
Paints and painting methods used on zinc (Z) coated steels are also suitable for ZA-coated steels. When painted surfaces require high surface quality, we recommend skin passed surface quality B.
All oils or impurities must be fully removed from the surfaces to be painted. To facilitate coating adhesion, the receiving plant can pre-treat zinc-based coated steels using zinc-phosphating or other suitable pretreatments.
Contact our corrosion resistance coating experts. We are eager to help you achieve longer-lasting coated steel surfaces.
