Hot-dip galvanized narrow strip with good corrosion resistance and excellent formability and processing properties.
Optimal corrosion protection – all-around protection, including at cut edges
Hot-dip galvanized narrow strip combines the advantages of batch and continuous galvanizing. The hot-rolled steel is zinc-coated continuously and, unlike conventionally hot-dip galvanized slit strip, its edges are also coated.
Narrow strip galvanizing: a brief explanation of the manufacturing process
Hot-dip galvanized narrow strip is produced by passing cleaned steel strip through a molten zinc bath. Before galvanizing, the steel strip is degreased, pickled, and annealed to ensure a clean, reactive surface. As it emerges from the zinc bath, a tightly bonded zinc coating forms on all sides, providing durable, all-around corrosion protection – even at cut edges.
Hot-dip galvanized narrow strip for a wide range of applications
As well as very good coating adhesion and outstanding corrosion resistance, hot-dip galvanized strip offers good forming properties, which are greatly influenced by the thickness of the zinc coating.
Its uses are many and varied: from gutter brackets and profiles with low coating weights and good formability, to roller shutter doors, building hardware, pipe brackets and barrel hoops with normal corrosion resistance and straightforward forming, to lightning conductors and grounding strips with increased corrosion protection and low formability requirements.
Available steel grades
| Steel family | Steel grade name |
|---|---|
| Mild steel for cold forming, DIN EN 10111 | DD11, DD12 |
| General structural steel, unalloyed, DIN EN 10025-2 | S185, S235, S275, S355 |
Further steel grades available by arrangement.
Available ordering groups and zinc coatings
| Zinc coating weight [g/m2] per side | ||
|---|---|---|
| Ordering group | Average value | Single spot test1 |
| Z120 | 120 | 95 |
| Z160 | 150 | 120 |
| Z226 | 225 | 180 |
| Z300 | 300 | 240 |
| Z400 | 400 | 320 |
| Z600 | 500 | 400 |
Ordering group for steel grades to DIN EN 10111, DIN EN 10025-2. The coating weights relate to one side in each case. | 1. Theoretical reference value for coating thicknesses per side on single spot samples in accordance with DIN EN 10346.
Sizes
| Product form | THICKNESS from_to in mm |
WIDTH from_to in mm |
LENGTH from_to in mm |
|---|---|---|---|
| Coils | 1.55 – 6.00 | 15 – 200 | – |
| Cut lengths | 1.55 – 6.00 | 15 – 120 | 500 – 7,500 |
Coils can be supplied with vertical or horizontal axis. For permissible dimensional variations, thickness and width, see product information.
Surface treatment for hot-dip galvanized narrow strip
Additional coating for temporary corrosion protection
Hot-dip galvanized narrow strip with an additional passivation layer provides reliable temporary corrosion protection. The passivation forms a thin protective film on the zinc surface, effectively shielding the material from moisture and significantly reducing the formation of white rust. As a result, storage and transport stability are improved while the metallic appearance of the steel strip is preserved. At the same time, formability remains unaffected, allowing further processing without restrictions. The passivated surface also serves as an excellent base for subsequent coating processes.
Product recommendation: chemical passivation
covex® T is a thin, transparent and colorless passivation coating that reliably protects metallurgically refined surfaces. It forms a fingerprint-resistant, Cr(III)-based protective layer and acts as a temporary barrier up to the first processing stage.
When stored and transported under appropriate conditions, covex® T provides effective protection against the formation of corrosion products and white rust for up to three months. This makes the coating ideal for sensitive metal surfaces that require temporary protection while maintaining their original visual appearance.
Hot-dip galvanized narrow strip – corrosion-resistant
Notes on the application and processing of hot-dip galvanized narrow strip
Corrosion protection
Applying a zinc coating to hot-rolled strip provides good general protection and ideal corrosion protection. The advantage of hot-dip galvanized narrow strip is that the edges are also coated. The protective effect is based on the relative positions of zinc and iron in the electrochemical series. As zinc is less noble than iron, it is attacked first by environmental influences such as humidity, sacrificing itself and preventing the oxidation process on the steel surface.
However, overall corrosion behavior depends on various factors, such as temperature, electrical conductivity of the electrolyte, and the thickness of the top coat. Corrosion behavior can only be assessed taking the interaction of all these factors into account separately for each different application.
In general, the thicker the zinc coating, the greater the corrosion protection.
Forming
Hot-dip galvanized narrow strip displays good forming proper-ties. When selecting the coating thickness it should be noted that formability improves with decreasing coating thickness. The choice of material is based on the forming requirements and the final shape of the workpiece. Forming dies need to be adapted because the zinc coating displays different physical properties. Draw-in radii and die clearances must be larger than for uncoa-ted material.
The use of sinter metals or specially treated die surfaces can reduce the risk of cold welding. Drawing lubricants are generally required when forming hot-dip galvanized narrow strip, and machine parameters such as blankholder force must be matched to the different flow properties of the coated material.
Joining
All thermal and mechanical joining methods can be used, as can adhesive bonding. However, the particular properties of the Z coat-ing require the processing parameters to be adapted compared with uncoated materials. Joining techniques which do not impair the surface of the strip and thus preserve the anticorrosion prop- erties of the coating include threaded connections, riveting and hemming. The problem of contact corrosion between different materials must be addressed on a case-to-case basis.
Welding
When using fusion welding processes, the zinc coating burns off locally in the weld zone, exposing the surface areas below, which then have no corrosion protection. Suitable post-treatment of the weld is required to counter environmental influences. Laser weld-ing has proven to be a very good fusion welding process due to its low heat input into the weld zone. Resistance welding methods can also be readily used because the original protection remains largely intact. However, compared with uncoated material, elec-trode force, electrode current and electrode cooling need to be adjusted to take the factors steel grade, strip thickness and zinc coating thickness into account.
Brazing
Hot-dip galvanized narrow strip is readily brazable. The great advantage of brazing is that the corrosion protection is retained in full because the vaporization temperature of zinc is higher than the melting points of soft and hard solder. The zinc coating must be treated with a suitable flux in preparation for brazing. Here too, the increased thickness of the coating must be taken into account.
Coating
An organic coating can be applied to the hot-dip galvanized narrow strip for enhanced corrosion protection and/or for decorative reasons. The zinc coating provides good adhesion properties, which can be further improved by a chemically passivated surface. Thorough cleaning with a special cleaning agent and activation of the surface are necessary to avoid adhesion problems.
