What Is Spangle on Galvanized Steel?

Spangle is a unique and desirable feature that appears on galvanized steel during the hot-dipped galvanizing process. It occurs when liquid zinc cools and solidifies, resulting in crystal grains forming on the steel’s surface. These crystal grains create a beautiful snowflake or hexagonal star appearance that adds visual appeal to the steel. That is spangle on galvanized steel.

The size, brightness, and topography of the spangle depend on various factors, including the composition of the zinc layer and the cooling method used during the galvanizing process. At Wanzhi Steel, we are able to offer big, regular, and zero spangle galvanized steel, giving you the flexibility to choose the look that best suits your needs. Contact us today for more information!

Types of Spangle on Galvanized Steel

According to American Standard (ASTM A653), it can be divided into galvanized steel with normal spangles (N), minimum spangles (M), and zinc-free spangles (F). Chinese standard (GB/T 2518) is similar to ASTM. While according to the European standard (EN10346:2015), the galvanized spangle can be divided into normal spangle (N) and minimized spangle (M). Japanese standard (JIS G3302) is close to the EU standard.

Standard	Chinese Standard (GB/T 2518)	American Standard (ASTM A653)	European Standard (EN10346:2015)	Japanese Standard (JIS G3302)
Steel Grade	DX51D+Z	DC51D+Z	DX51D+Z	SGCC
Code	N (normal spangle)	N (normal spangle)	N (normal spangle)	R (regular spangle)
Definition	Do not control the solidification process of the zinc layer to form various sizes of spangles during the natural solidification process.		Spangles are obtained when the zinc coating is naturally solidified. There will be spangles of different sizes and brightness. But the quality of the galvanized layer will not be affected.	Spangles formed during the crystallization and solidification of the zinc layer.
Code	M (minimum spangle)	M (minimum spangle)	M (minimized spangle)
Definition	Control the solidification process of the zinc layer to obtain relatively uniform and small spangles, which are still visible to the naked eye.		Fine spangles are obtained by controlling the solidification process of the zinc layer in a special way. Usually, the spangles are invisible to the naked eye.
Code	F (zinc-free spangle)	F (zinc-free spangle)		Z (zero spangles)
Definition	Tiny spangles are invisible to the naked eye by controlling the solidification process of the zinc layer.			To control normal spangle formation to a small value.

Different Applications of Galvanized Metal with Spangle

In fact, spangles only offer different surface appearances. But it will not influence the quality of zinc coating. However, as the base metal of prepainted galvanized steel coil, spangles will influence its painting adhesion and corrosion resistance. Therefore, small or zero-spangle products are better for the home appliance and automobile industries. While galvanized steel with normal spangle is often for general purposes and the construction industry. If you have special requirements for spangles, please inform the supplier in advance.

What Will Affect Spangle Size?

There are many factors that affect the size of the spangle, for example,

(1) Base metal: The thicker the base metal, the smaller the surface roughness and the larger the spangle.

(2) Cooling speed: The faster the cooling speed, the shorter the crystal growth time and the smaller the spangle.

(3) Number of nuclei: The crystal grains are formed on the steel base, the more nuclei, the smaller the spangles.

(4) Other factors (production environment, cooling temperatures, etc.).

How to Get Minimum Spangles?

When the zinc liquid is close to the solidification temperature, spray water droplets with a diameter of less than 0.1 mm onto the surface of the galvanized sheet immediately. Then it will form small and uniform crystalline nuclei, which will help to form small spangles. Then go through skin-pass rolling with a reduction of less than 1% to get smooth spangles. Minimum spangles are suitable for painting purposes, and smooth spangles are suitable for deep drawing.

Shape of Spangles

The shape of the spangle depends on the type of alloy added to the zinc solution. For example, adding lead and antimony will form phoenix-shaped spangles. While adding lead and tin will produce fern-shaped spangles and so on.

The different appearances will influence the processing method. For example, in the case of drawing and deep drawing, the processability of the feather spangle is the best, followed by the fern spangle and the leaf spangle. While during bending and tension processing, the leaf spangle is the best, followed by the feather spangle and the fern spangle.

Uneven Spangles

The uneven spangle is a surface defect of hot-dip galvanized products. Although it will not affect the use of most products, it will impact the appearance of the surface. But sometimes the uneven spangles will cause poor adhesion of the zinc layer, which directly affects the use of galvanized steel. The uneven spangles can be summarized as follows:

(1) There are spangles on one side, and the diameter is about 6mm. While there are no spangles on the other side.
(2) Along the longitudinal direction of the galvanized strip, the size of the spangle shows regular fluctuations.
(3) Along the transverse direction of the strip, the spangles on one side are large, and the spangles on the other side are small.
(4) The spangles on the edge of the strip are small, while the spangles in the middle are large.

Conclusion

Wanzhi Steel is a leading galvanized steel manufacturer in China, with 2 hot-dip galvanizing lines at our factory. Our extensive range of products includes high-quality galvanized steel coils, sheets, and strips with regular spangles, small spangles, and zero spangles. And HDG products are with a zinc coating range of 30-275 g/m2. At Wanzhi Steel, we understand the importance of maintaining high standards, which is why we have a rigorous quality control system in place. Additionally, we welcome third-party quality inspections.

If you’re looking for a reliable and experienced galvanized steel manufacturer in China, look no further than Wanzhi Steel. Get in touch with us today for more details. We’re always happy to help!