All of the growth supports by FassadenGrün conform to the standard "Stainless Steel - Rust-Free", suited for the exteriors. This is not self-evident, as you will learn in the following section. However, rust may occur even in the case of stainless steel. Sometimes, it is recommended to use only medium kits "Premium", or massive kits conforming to the standard "A4", or "V4A" (AISI 316). You will get more information on this site.
FassadenGrün choses stainless steel types for growth supports, which are approved for the use in exterior building in Germany. This means, these types of steel are sufficiently corrosion-proof and do not show signs of embrittling or material fatigue in the case of frost, under normal circumstances. Usually, these are steels of the material groups AS (1.4301) and A4 (1.4401 and 1.4404), at least A2, or - in the case of other than DIN-label - equal materials. Stainless steel cable/wire rope is sold only in the high quality A4, as well as the corresponding U-clamps. Medium kits "Premium" and massive kits provide the high standard "V4A".
The Nirosta-steels A2 (V2A) and A4 (V4A) used by FassadenGrün are hardy and therefore difficult to work or cut. This means the tools might tear earlier and need to be exchanged in the process of milling the grooves for the cross holders, for instance. The process is also only possible on particularly heavy, vibration-rigid machines, resulting in higher prices.
Due to the dangers, some providers use a type of stainless steel for brackets, which can be processed without high toll attrition (1.4305). On the Thyssen-Krupp and DEW check list on the use of this material - called "Nirocut" - it is indicated, due to "experiences with damage events", that this kind of steel is approved for "decorative pieces", not for tractive, or pressure fraught elements in the exteriors, though. It embrittles at temperatures below 0 degree and becomes fragile. This particularly applies to highly fraught head bars of cross holders. This type of stainless steel does not reach the A2 corrosion resistance. This is why FassadenGrün does not supply parts processed of this type of stainless steel, despite of possible savings.
Stainless steel parts can be both, magnetic and non-magnetic! We once had a complaint on eyebolts with the explanation they were not made of stainless steel because of their magnetism. The inquiry revealed: Stainless steel is not magnetic, because the magnetic characteristics in the wires, rods, or bars vanish caused by the common heat treatment (for instance "stress relief heat treatment"). Resulting from some further processing coming along with structural change of the stainless steel, like for instance tightening, thread rolling, bending and so forth, "strain hardening" might occur and therewith the re-occurence of magnetic characteristics. These do not affect the corrosion resistance.
Why are there even more expensive types, like A4, next to the "normal" stainless steel A2? There is a well-known saying from the metalworking shops: "A2 does not rust - A4 definitely not at all." Although this answer is quite striking - the stainless steel type A4 is not necessary, actually -it requires nevertheless the addition. In the case of growth support, it becomes apparent, that the material quality A2 is sufficient in about 98% of the cases in the private section. In the following problem cases it might indeed come to discolouration, in extreme cases even to rust, pitting and so forth, which is why medium kits "Premium", or "massive kits" should be oftentimes chosen. That way, function and their shiny appearance remain even under extreme conditions.
Saline air near the coast may lead to deposits on stainless steel and furthermore even to discolourations and rust, occasionally. Mostly it is already known in these regions, that even stainless steel does rust. In these cases, A4 must be used. Additionally, the growth supports need to be cleansed by hosing with freshwater (drinking water) 2-3 times a year. Also, a deficient roof protrusion and thereby a regular wetting with rainwater (self-cleaning) is advantageous.
Exhaust gas in the air in industrial areas and by much-frequented auto arteries ("acid rain") might also lead to discolourations and rust. The statement under 01 applies to these cases, as well.
Flash rust often emerges from abrasion of common steel, whereby the little particles rust instantly in humid air, and are placed on stainless steel as rust infection. These particles then generate discolourations, as well as pitting, like a catalyzer. Ferric abrasion does emerge particularly by tracks, especially on train stations, sidings and so forth, and by heavily travelled streets, where braking and starting take place and a lot of iron is rubbed off. Also, metal works are quite problematic, whenever rubbed off iron is scatted through the air, due to filing, grinding, cutting and so forth. Even in the course of abrasive cutting of stainless steel wire, the flying, glowing particles might lose their rust resistance and operate as rust “germs”! The statement under 01 applies to these cases, as well.
Splashes might contain iron salts as well. If those get on stainless steel, they might lead to rust, both on smooth surfaces and in capillaries of threads. Acidic and ferrous detergents and fertilisers, occasionally de-icing salts are problematic. Water already containing dissolved rust is especially critical. A single, rusting screw used somewhere in the upper area of the system, might have a deleterious effect, if it dispenses its rust-within to the rain- or condensation water and scatters it on the climbing system below via a dripping corner or edge. In this case, the statement under 01 applies, as well.
Stainless steel components (for instance crossheads from FassadenGrün) must not be used along with low-grade materials (for example zinc-coated wires and zinc-coated thread rods), because this might lead to contact corrosion. It is also important to only use high-grade jaw spanners and forceps with the label "Chrom-Vanadium" for the mounting, in order to not ream low-grade iron, which might cause discolouration and rust, later on. Binding materials with iron wire act corrosively, as well, and are therefore to be avoided.
When rust problems occur, it is assumed, initially, that they were caused by a ONE-time action. The rust parts then are treated with a customary stainless steel cleaner. That way dirt and flash rust particles will be removed and washed away.
In the case of advanced corrosion it is recommended to remove the afflicted parts. Simply brushing with a brass- or stainless steel wire brush would not be sufficient. Between the cleansings, the afflicted parts must be polished with the help of 2-3 kinds of sandpaper, starting with a 120s, or 240s grain, ending with a 600s, or 1200s one. In order to reach into the (thread) furrows, simply crease the sandpaper. Please contact us, if necessary, we will provide the utensils.
If this does not permanently lead to success, the brackets need to be replaced by A4 types, meaning WM 08133, or WM 12153. It is always suggestive, though, to detect the cause of the rust and remove it, if possible.
High grade stainless steel wire ropes need high grade stainless steel holders. If inferior galvanised steel mounts are used, there may be rust problems at the contact areas. On the other hand, the opposite is possible. For instance, mounts and holders from FassadenGrün are combinable with zinc coated grids or lattices because the mass (and "potential") of the inferior metal is much larger than that of the high grade metal. This way, the galvanised grid is not attacked by electrolytic corrosion. Another possibility is to lay a thin stainless steel wire rope through a massive galvanised supporting mount (high "potential") - no problem. Another example is the famous tiny, high grade, steel screw in the huge, galvanised support.- nothing will rust. However, a tiny galvanised screw in a large, high grade, steel support or beam (see photo), and you get massive rust marks that spread over to the high grade stainless steel.