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Stainless Steel - Characteristics, Selection, and Rust

All growth supports/trellises from FassadenGrün conform to the standard "Stainless Steel--Rust-Free" for outdoor use. This is not self-evident, as you will learn in the following section. Rust can occur, however even in the case of stainless steel, and we'll address that in this section; in some cases, we recommend using only the "Premium" Medium Kit or Massive Kit that meet the standard "A4" or "V4A" (AISI 316). You will find more information here.

Stainless Steel from FassadenGrün

For trellises/climbing supports, FrassadenGrün selects grades of stainless steel that are approved in Germany for outdoor use in construction. That is, under normal conditions, these types of steel are sufficiently corrosion resistant and do not exhibit embrittlement or material fatigue, even in frost. 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 -- materials of equal value. Stainless steel cable/wire rope, as well as the corresponding U-clamps, are sold only in the high quality A4. The Medium Kit "Premium" and Massive Kits provide the high standard "V4A."

Disadvantages of Stainless Steel V2A and V4A (AISI 304 and 316)

The Nirosta (non-rust) steels A2 (V2A) and A4 (V4A) used by FassadenGrün are hardy and therefore difficult to work or cut. That is, tools might wear out or need to be changed in the process of milling the grooves for the cross holders, for instance. The process is also only possible on particularly heavy, vibration-resistant machines, resulting in a higher price mark.

Dangers Associated with Stainless Steel 1.4305 (A1, or V1A)

For this reason, some suppliers use a type of stainless steel for mounts which can be processed without high tool attrition (1.4305). According to the Thyssen-Krupp and DEW check list on the use of this material (called there "Nirocut"), because of "cases of damage/injury," this kind of steel is approved only for "decorative pieces," not for tensile and pressure-loaded elements in outdoor areas. It embrittles at temperatures below 0 degrees Celsius and is prone to breakage. This particularly applies to heavily loaded head bars of cross mounts. This type of stainless steel does not reach the corrosion resistance of A2. This is why FassadenGrün does not supply parts made of this type of stainless steel, despite possible savings.

Stainless Steel and Magnetism

Stainless steel parts can be both magnetic and non-magnetic! We once received a complaint about eyebolts with the claim that they were not made of stainless steel because of their magnetism. The research revealed: stainless steel is not magnetic, because the usual heat treatments in the steelworks (stress relief 'annealing') eliminate the magnetic properties in the wires, rods, or bars. As a result of some further processing associated with micro-structural change of the stainless steel (tightening, thread rolling, bending, etc..), "strain hardening" might occur and therewith the recurrence of magnetic characteristics. These do not affect the corrosion resistance.

When to Use V4A / AISI 316?

Why are there even more expensive types, like A4, in addition to the "normal" stainless steel A2? A winged word (well known saying) from the metalworker reads: "A2 does not rust -- A4 definitely not at all." As striking as this statement sounds, the stainless steel type A4 is not really necessary! In the case of climbing aids/trellises, it becomes apparent that the material quality A2 is sufficient in about 98% of cases in the private sector. In the exceptional problem cases mentioned below, however, discolouration and, in extreme cases rust, pitting, etc.. are possible with A2, which is why the Medium Kit "Premium" or Massive Kits may sometimes be the best choice. This ensures functionality and a lustrous appearance even under extreme conditions.

Problem Case 01: Salt

Saline air near the coast may lead to deposits on stainless steel and occasionally to discolourations and rust. Mostly it is already known in these regions, that even stainless steel does rust. In these cases, A4 must be used. Additionally, the trellises/growth supports need to be cleansed 2-3 times a year by hosing/spraying with fresh water (drinking water) 2-3 times a year. Even a missing roof overhang which could provide a regular wetting with rainwater (self-cleaning) is advantageous.

Problem Case 02: Exhaust Gases

Exhaust gas in the air in industrial areas and by heavily traveled traffic routes (causing "acid rain") might also lead to discolourations and rust. The description in problem case 01 applies to these cases as well.

Problem Case 03: Flash Rust

Flash rust (rust that occurs quickly-- even overnight) often arises from abrasion of ordinary steel, whereby the tiny particles rust instantly in humid air, precipitate on stainless steel as rust germs, and like a catalyst, produce discolouration, pitting, and surface fouling. Ferric (iron) abrasion occurs mainly on railway lines, especially at railway stations, shunting tracks/sidings, etc.. and by heavily travelled streets, where braking and starting take place and a lot of iron is "rubbed off." The use of decorative "precious" rust in architecture and facade design, in trellises in the garden, etc.. can also cause flash rust. Metal work (grinding, filing, flexing, etc..) is also problematic, as abraded ('rubbed off') iron is then scattered through the air. Even when cutting wire rope from stainless steel, the flying, glowing particles can lose their rust resistance and then act as rust germs! This is so in the previous problem case- 01.  

 

 

Problem Case 04: Tainted Splash Water

Water splashes may contain iron salts as well. If these get on stainless steel, they can lead to rust, both on smooth surfaces and in the capillaries of threads. Acidic and ferrous detergents and fertilisers, and possibly also 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 can be devasatating if it dumps its rust 'cargo' into rain- or condensation water and distributes it to the climbing system below via a dripping corner or edge. Again, what is described in problem case 01 applies. 

Problem Case 05: Differences in Material

Stainless steel components (e.g. FassadenGrün crossheads) should not be used/installed with low-grade materials (for example, galvanised wires and galvanized threaded rods), as this leads to contact corrosion. It is also important that only high-grade open-ended wrenches and pliers (marked "Chrom-Vanadium") are used for assembly/mounting, in order not to "rub" off any low-grade iron, which can lead to discolouration and rust later on. Binding materials with iron wire are corrosive as well, and should be totally avoided.

Help in the Case of Rust Problems

When rust problems occur, the first assumption is that they were caused by a one-time action. The rusted parts are then treated with a standard commercial stainless steel cleaner to dissolve and wash away impurities and flash rust particles.

In the case of advanced corrosion, it is best to remove the affected parts. Simply brushing with a brass- or stainless steel wire brush (or steel wool) is not enough. Between two cleansings, the affected areas must be polished with the help of 2 - 3 kinds of sandpaper, starting with 120 or 240 grit, followed with 600 or 1200 grit. To reach into the (thread) furrows, simply crease the sandpaper. Please contact us if you need assistance; we can provide the utensils. 

If this does not bring lasting success, the mounts need to be replaced by A4 types (so, WM 08133, or WM 12153). And naturally, it is best to determine the cause of the rust and where possible, to remove it. 

Stainless steel climbing trellis made of wire rope for clematis
Stainless Steel Lattice for Clematis
Due to increased contact with electrolytes (sluiced out/washed out plant substances) and slowed drying, galvanized eyebolts on climbing trellises corrode even faster in climbing aids than in the open air.
Galvanised Steel -- Rust
Other galvanised (zinc-coated) wire supplies are also affected by accelerated corrosion.
Rust on Galvanised Metal
With low-grade stainless steels not intended for outdoor use, discolouration often occurs on larger areas shortly after mounting.
Discolouration of Stainless Steel
Discolouration on a cross mount after contact with rusting iron (wire as binding material).
Rust on Stainless Steel
Tiny rust marks on a cover disc and nut as a result of installation with a low-grade open-end wrench.
Rust Marks on Stainless Steel
Sometimes only 1 or 2 tiny filings, or sawdust of "normal" iron from the abrasive cutting of a stainless steel wire, are enough to cause rust, like in these threads of cross mount WH 10141!
Stainless Steel A2 with Rust Marks

Combining "Stainless Steel" and "Galvanised" Materials

High grade stainless steel wire ropes need high grade stainless steel mounts/holders. If inferior galvanized (zinc-coated) steel mounts are used, there may be corrosion and rust problems at the contact areas. But the opposite is also possible. For instance, mounts and holders from FassadenGrün are combinable with galvanised 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 rust problem. Another example is the famous tiny, high grade, steel screw in the huge, galvanised support-- also here nothing will rust. However, have even a tiny galvanised screw in a large, high grade, steel support or beam (see photo), and you get massive corrosion/rust formation that immediately spreads over to the high grade stainless steel.

Small galvanised screw in a large stainless steel lamp = massive corrosion!
Combining "Stainless Steel" and "Galvanised" Metal