Surfaces, but not superficial
Depending on the use, there are very many surface coatings. Here are some standard procedures:
The most affordable surface coating is galvanisation. It protects springs for many years, even against heavy weathering. However, the fatigue strength is shorter with galvanised springs.
Blue galvanised springs:
In new condition they have a bright, shiny surface, which becomes matt over time.
For this, we recommend:
Nickel-plated surfaces: This still relatively inexpensive surface treatment is more resistant and permanently pearlised grey. These two processes are highly suited to mass production.
In contrast to:
Chromium-plated surfaces: These are expensive, but highly polished and long-lasting. They are less suited to mass production. But this coating too makes the spring steel become brittle and is therefore unsuitable for dynamic highly stressed springs.
They have the advantages that they do not have a negative impact on fatigue strength, they are very corrosion- and acid-resistant and can be supplied in all colours.
For example, the polyester resin coating, as used on chassis springs, is particularly resistant. Teflon-coated springs are very similar, which also have very good slip properties.
These examples are just a small selection of the wide variety of surfaces.
All Knörzer compressions, tension and rotational springs are given a final heat treatment as standard according to regulations that have proved their worth in practice. In the process, great hardness and fatigue strength is generated.
Springs can be specially treated for extreme uses (e.g. high working temperatures). The stacks of compression and tension springs sold by the metre are not given a final heat treatment as standard.
Shot blasting strengthens and compacts the surface, smooths out traces of processing and greatly increases fatigue strength. Because the wire surface is subject to the most stress in springs, shot blasting is essential for dynamically high-stressed springs.
It also improves the corrosion-resistance of stainless steel springs. Almost all springs can be shot blasted. With the help of a range of modern blasting plants, we can cover a broad spectrum and achieve results in surface treatment that far exceed conventions standards.