Surface coating

Circlips must be without burr. Circlips are normally supplied corrosion in accordance with tabe 4 (at manufacturer's discretion). No special details.

Concerning this condition on delivery must be stated in the designation of a circlip.

1) Phosphatized and oiled according to DIN 50942 Symb r---f and blackened and oiled (thermally or chemically) = No sign of corrosion permissible after 8 hours.

Of exposure to salt spray according to DIN 50021-SS.

If a particular anti-corrosion treatment is required which is different from table 4, the designation of the circlips must be supplemented accordingly. For plating, the symbols

According to DIN 267 Part 9 apply, e.g.: Circlips in a drum or bell, it is not possible to maintain closely tolerance plating thickness.

Attention is drawn to DIN 267 Part 9 regarding the danger of hydrogen-induced delayed brittle fractures in the case of circlips with electroplated surface protection.

The upper limit of the circlips thickness may be exceeded according to the film thickness of the plating required in the case of circlips with electroplated surface prtection. This must be taken into account when designing the groove.

Alternatively we offer:

What is Microcor®?
Microcor® is made up of layers of < 25y thickness applied to ensure cathodic protection against corrosion of a min. 480 SST in accordance with DIN 50021 SS and/or 5 rounds of Kesternich testing in accordance with DIN 50018 SFW 2.0 S.
For this purpose a number of different materials whose composition, type of application or use profile of their dry film are optimally tailored to the on the items to be coated. The typical composition of microcor® is an inorganic, metal-pigmented prime coat and an organic outer layer.

Microcor® prime coat
Microcor® prime coat is not a paint as such, but instead a thermo-reactive system made up of zinc and aluminium lamellae. These produce a silver-metallic layer that is highly resistant to corrosion. It contains no organic resins, as the coating must be electrically conductive to provide cathodic corrosion protection.

The burned-in dry film consists of approx. 85% metal in the form of zinc and aluminium particles. The interstices are filled with inorganic particles, providing protection over the entire coated surface.

The high degree of resistance evidenced in salt spray testing compared to galvanic zinc coatings is explained by what is known as the “barrier effect”. Corrosive substances such as oxygen and moisture have to attack every single one of the fish-scale-like layers of lamellae, substantially slowing down the corrosion process versus the compact metal coating of a galvanized surface.

The materials used contain no harmful heavy metals such as cadmium or chromium. Neither are any carcinogenic, mutative or teteragenic substances present. Coated locking rings may thus be further processed without any safety concerns. Temperature resistance of up to 250 degrees allows for unrestricted use even in the encapsulated interiors of engines.

Microcor® outer layers
Microcor® is a highly cross-linked organic sealant/additional coating to be applied to a prime coat. The annealing process results in the formation of a thin, non-porous, chemical resistant film. In contrast to priming, this layer is electrically insulating, thus providing effective protection against contact corrosion. In addition it offers:

• Excellent bonding
• Very high abrasion resistance
• Low annealing temperatures < 200°C
• Excellent performance in Kesternich testing in combination with prime coat
• Superb flexibility
• No physiological danger

Pre-treatment of locking rings

A thorough and precise pre-treatment is necessary to obtain optimal corrosion protection and bonding of the coating to the subsurface.

Fine crystalline zinc phosphating is the most widespread method for pre-treating items delivered in a wide variety of different conditions in a consistent fashion so as to ensure uniform quality. After degreasing, the objects are phosphated in a drum or immersion bath and then allowed to dry. The phosphate coating provides both protection against storage corrosion and superb bonding with subsequent coatings. This process has a substantial positive effect in terms of coverage and accumulation of coating material, especially around edges (such as with sharp-cornered stamping surfaces).

Centrifuging
Smaller bulk items like our locking rings are processed effectively in coating centrifuges. First they are dumped into coating buckets, then dipped into the material batch container. After wetting the items a carriage transports the bucket into the centrifuge itself. Centrifugal force spins off extra material in pre-programmed amounts. Finally, the items are put on an annealing conveyor belt via vibrating feeder where the applied coating is burned in. Number of revolutions, centrifuge time and the viscosity of the coating material determine the coating thickness obtained. Our locking rings come with a standard coating of 10 my for a rust-resistance factor of approx. 120 hrs. in salt spray (fog) testing. Due to the locking rings’ geometry it sometimes occurs that deposits form; our many years of experience have taught us that these deposits can be reduced to a minimum at a coating thickness of 10 my and less (these deposits are a purely aesthetic problem). Greater layer thicknesses affording better corrosion protection are of course available, however these result in an increased likelihood of deposits, which cannot be considered a defect.


Microcor® and the environment

Let us once again summarise: no harmful heavy metals are present in either the prime coat or the outer coatings, nor any carcinogenic (cancer-causing), mutative (reproductively harmful) or teteragenic (organ-damaging) substances. The approval for use in the food industry further attests to their health safety. Coated parts may thus be handled in any fashion without concern. The solvents created during processing -- mainly aromatised alcohols -- are collected, concentrated and broken down by ionisation. Pre-treatment is done as described on either a mechanical or aqueous basis, without the use of any substances harmful to the environment.

Microcor® is ideally suited for all types of parts that may be damaged by embrittlement but still have to provide adequate protection from corrosion. These surface coatings are used primarily in the automotive industry, as indicated by the wide range of approvals and specifications from the following firms:
BMW; Bosch; Ford; ITT/ATE; Knorr, Mercedes, Opel, Porsche, Stabilus; VW; VDA; MAN
(details on approvals and specifications may be requested)