In order that standard components can function for long periods, without maintenance and reliably even under extreme operating conditions, the Schaeffler Group has developed several coatings for such requirements.

These coatings increase the corrosion resistance and/or wear resistance of the surface.

The selection of the coating is always dependent on the area of operation and the application.

Components at risk of corrosion are protected by:

• Corrotect^® special coating, link
• Protect A thin film chomium plating, link
• Protect B thin film chomium plating, link.

The high hardness of the thin film chromium plating and the special surface structure give an anti-wear effect. The columnar structure has a certain capacity for storage of lubricant. This ensures adequate lubricant in the rolling element contact zone even under extreme environmental and operating conditions.

A particularly high level of wear resistance together with a very high anti-corrosion effect is achieved by the coating Protect B, which has an additional layer of chromium mixed oxide. Due to its surface quality, this ensures separation of the contact between the rolling element and hard chromium layer and thus gives emergency running characteristics and reduction of wear under extreme operating conditions. Even under highly unfavourable environmental conditions, this coating still acts in a supportive capacity to the lubricant. Since the coating increases the wear resistance of the base material, the preload is maintained over an extended period.

For use in the food industry, compliance with exacting environmental and health conditions must be achieved. The coating Protect A is free from Cr(VI) and can therefore be used in this sector.

Corrotect^® is a surface coating applied by electroplating, Figure 1. It is an extremely thin anti-corrosion coating with cathodic protection and black chromate passivation. Under load, it is compacted into the surface roughness profile and partially worn away.

In parts coated with Corrotect^®, running-in occurs in the area of the seal and an optically bright area develops as a result. Due to the remote cathodic protection mechanism, formation of rust in this area can also be prevented.

The special coating Corrotect^®:

• is resistant to moisture, salt spray mist, contaminated water and weak alkaline or weak acidic cleaning agents
• does not impair the load carrying capacity, in contrast to the use of corrosion-resistant steels
• is extremely resistant to corrosion
• offers protection against rust on all surfaces
• ensures rust protection of smaller bright spots due to its cathodic protection effect
• gives protection against EP additives
• has good thermal conductivity.

For application in the food industry, the Schaeffler Group also offers the special coating Corrotect^® in a Cr(VI)-free version, Figure 2.

The Cr(VI)-free special coating Corrotect^® fulfils the RoHS  requirements in accordance with EU Guideline 2002/95/EG. All other advantages are identical with the standard Corrotect^® coating, see page link.

Components coated with Corrotect^® are particularly suitable where corrosion resistance is the most important factor.

The coating is also used very successfully to prevent adhesion of weld spray.

The following products in the field of linear motion are available with the Corrotect^® coating:

• linear recirculating roller bearing and guideway assemblies RUE..-E (-L-KT)
• linear recirculating ball bearing and guideway assemblies KUVE..-B (-KT)
• shafts W
• hollow shafts WH
• guideways LFSR
• profiled track rollers LFR
• linear ball bearings KB, KS, KH.

Components with the Corrotect^® coating containing Cr(VI) have the suffix RRF; components with the Corrotect^® coating free from Cr(VI) have the suffix RROC; see Ordering designation.

The ordering designation for a recirculating ball guidance system KUVE25-B with two carriages, accuracy G3 and preload class V1 and the Corrotect^® coating containing Cr(VI) is:

• KUVE25-B-W2-G3-V1-RRF/

The ordering designation for a recirculating ball guidance system KUVE45-B-KT with one carriage, accuracy G2 and preload class V1 and the Corrotect^® coating free from Cr(VI) is:

• KUVE45-B-KT-W1-G2-V1-RROC/

The table shows technical/physical data for the special coating Corrotect^®.

Protect A is a pure chromium layer with a columnar surface structure, Figure 3.

The coating is applied by electroplating. The parts to be coated are heated to approx. +50 °C. Since no structural changes occur, the parts retain full dimensional stability.

The matt grey chromium layer retains a certain amount of lubricant between the pearls. As a result, effective anti-wear protection is achieved even under mixed friction or slippage conditions.

The temperature range of the guidance system is between –10 °C and +100 °C.

The coating:

• is resistant to various chlorides, various oils, sulphur compounds, chlorine compounds and weak acidic media
• does not influence the load carrying capacity and operating life of the coated products
• has higher wear resistance due to its high hardness
• ensures effective anti-wear protection even under mixed friction conditions
• offers good protection against EP additives
• has good thermal conductivity
• is moderately resistant to corrosion
• prevents false brinelling under vibration while stationary
• is free from Cr(VI).

Protect A does not contain Cr(VI). Components with this coating are therefore particularly suitable for use in the food industry, medical equipment and similar areas.

The coating is recommended for use under particularly small stroke lengths and vibration while stationary.

The following products in the field of linear motion are available coated with Protect A:

• linear recirculating roller bearing and guideway assemblies RUE..-E (-L-KT)
• linear recirculating ball bearing and guideway assemblies KUVE..-B (-KT).

Other products in the shaft and track roller range are available by agreement with the Protect A coating.

Components coated with Protect A have the suffix KD; see Ordering designation.

The ordering designation for a Protect A-coated recirculating ball guidance system KUVE25-B with two carriages, accuracy G3 and preload class V1 is:

• KUVE25-B-W2-G3-V1-KD/

The table shows technical/physical data for the special coating Protect A.

When using Protect A, coated carriages and coated guideways must always be combined. If coated carriages are used with uncoated guideways, for example, this will lead to a reduction in preload.

Protect B comprises two layers: a thin film chromium plating (Protect A) is covered by chromium mixed oxide, Figure 4.

The corrosion resistance is provided by the chromium mixed oxide layer. This layer acts in a supportive capacity to the lubricant when used in aggressive atmospheres and at high temperatures.

The temperature range of the guidance system is between –10 °C and +100 °C.

The coating:

• is resistant to various chlorides, various oils, sulphur compounds, chlorine compounds and weak acidic media
• does not influence the load carrying capacity and operating life of the coated products
• improves the running-in behaviour
• offers effective anti-wear protection under inadequate lubrication
• offers good protection against EP additives
• acts in a supportive capacity to the lubricant by mean of the second layer in aggressive atmospheres and at high temperatures
• has good thermal conductivity
• offers high anti-wear protection together with high anti-corrosion protection
• prevents false brinelling under vibration while stationary.

Where high requirements for anti-corrosion protection are present and continuous lubrication cannot be ensured, Protect B is the suitable coating.

The following products in the field of linear motion are available coated with Protect B:

• linear recirculating roller bearing and guideway assemblies RUE..-E (-L-KT)
• linear recirculating ball bearing and guideway assemblies KUVE..-B (-KT).

Other products in the shaft and track roller range are available by agreement.

Components coated with Protect B have the suffix KDC; see Ordering designation.

The ordering designation for a Protect B-coated recirculating ball guidance system KUVE25-B with two carriages, accuracy G3 and preload class V1 is:

• KUVE25-B-W2-G3-V1-KDC/

The table shows technical/physical data for the special coating Protect B.

When using Protect B, coated carriages and coated guideways must always be combined. If coated carriages are used with uncoated guideways, for example, this will lead to a reduction in preload.