Highest corrosion protection for the photovoltaic industry

edited by Wuppermann AG

Leverkusen - Germany

Wuppermann is the only company in Europe that can produce strip steel with runs of up to 1200 g/m² in pure zinc and 1000 g/m² in zinc-magnesium - optionally with powder coating. The high Z (Zinc) and ZM (Zinc-Magnesium) coatings open up undreamt-of possibilities for the harshest environmental conditions or piling profiles in the photovoltaic industry.

Strip galvanized steel offers durability and best corrosion protection

The requirements for mounting systems in photovoltaic plants are extremely diverse: in addition to the different types of plants, such as ground-mounted or roof-mounted, the statics, design and durability of a structure also play a decisive role in the planning of a base frame. The base material steel, provided with long-lasting corrosion protection, manages this “balancing act of requirements” effortlessly. Wuppermann offers high-quality and resistant products for solar park designers and operators. These include galvanized strip steel and processed semi-finished products such as galvanized piling profiles, support tubes and C-rails. Wuppermann uses high zinc coatings (Z) as well as alloys of zinc, magnesium and aluminium (ZM).

Wuppermann produces strip steel with runs of 1200 g/m² in pure zinc and 1000 g/m² in zinc-magnesium

The standard for corrosion protection (DIN 55634-1) takes into account runs up to 600 g/m² for pure zinc (Z) and 430 g/m² for zinc-magnesium (ZM). But with these values, the production possibilities are by no means exhausted. In the strip galvanizing plant of Wuppermann in Judenburg, Styria, runs of up to 1200 g/m² in pure zinc and 1000 g/m² in zinc-magnesium (Wuppermann Zink-Magnesium, short: Wzm) are producedoptionally with powder coating. This makes Wuppermann the only company in Europe that can produce such high Z and ZM runs. The high Z and ZM coatings open up undreamt-of possibilities for the harshest environmental conditions or piling profiles. Even relatively new designs such as floating solar plants or agro-photovoltaic systems, where solar plants are installed on agricultural land, have particularly high requirements for corrosion resistance. In the case of floating, the steel is exposed to an increased salt and/or moisture content in the ambient air, and in the case of agro-photovoltaics, the fertiliser places particular demands on the steel. In addition, areas that have been contaminated by different previous uses are increasingly being used to produce renewable energy and are being upgraded accordingly. Steel coated with high zinc or zinc-magnesium coatings, such as Wuppermann Zink-Magnesium, is predestined for these applications.

Short delivery times and flexibility for fast realization of PV projects

Orders in the PV industry are often project business and involve complex approval procedures. As soon as all approvals have been obtained, fast implementation is required. This means short delivery times, absolute adherence to deadlines and high flexibility. The individual parts have to be delivered “just-in-time”, in the right quantity and sequence according to the construction progress. In addition, the driven posts are the first components of the substructure to be installed in a solar park. These logistical peculiarities can be mastered through narrowest cooperation of a very experienced team at Wuppermann with the client. This also allows exceptionally short delivery times of 14 days to be realized.

The popularity of zinc-magnesium is growing steadily

In addition to the classic pure zinc coating, an alloy of zinc, magnesium and aluminium (ZM) is increasingly used. Different proportions of magnesium (Mg) and aluminium (Al) have different effects on the properties of the alloy and ultimately determine the area of application. For the partly very heterogeneous requirement conditions in the PV industry, an alloy composition with a slightly higher proportion of Mg and Al (about 3% each) than the most corrosion-resistant one has been found. Standardised laboratory tests and knowledge gained from practical experience in the meantime certify that this ZM alloy has about twice the corrosion resistance of pure zinc.

Advantages of continuous strip galvanizing for the PV industry

As early as 1989, Wuppermann developed what was then a new technology for galvanizing hot-rolled strip steel, thus laying a foundation stone for today’s continuous hot-dip galvanizing of hot strip.

In this process, the continuously welded steel strip is fed through the pre-treatment and melting bath at a constant speed. The hot strip is heated to galvanizing temperature only shortly before the dip bath. The wetting time in the melt is only a few seconds with the effect of a very uniform pure zinc coating. A stripping nozzle system directly after the zinc bath ensures, in accordance with customer requirements, a constant coating thickness and a very homogeneous surface structure over the entire strip length. The final slitting of the galvanized wide strip, subsequent hole punching and cutting to length, results in bright, ungalvanized cut surfaces. However, corrosion on the exposed steel core at the outer edges and the punched holes is insignificant up to a strip thickness of approx. 1.50 mm. This is explained by the cathodic protection effect. In this electrochemical process, the less noble metal zinc goes into solution as a “sacrificial anode”, while the steel itself remains undamaged.

As an option to galvanized slit strip, Wuppermann Austria also produces slit strip with fully galvanized longitudinal edges up to a strip width of 410 mm. Piles made of this material are thus even better protected against corrosion, especially in the particularly vulnerable soil-air transition. ‹