The “ VW TL 52132 Lubricants for Threaded Connectors - Requirements” standard, developed by the Volkswagen automotive company , describes the requirements for lubricants used in threaded connectors. According to this standard, the types of surface protection with lubricants are listed in the “VW 13750 Surface Protection for Metal Parts - Surface Protection Types, Codes” standard. The VW TL 52502 standard applies to aluminum threaded connectors.
The requirements of the VW TL 52132 standard are explained under the following headings:
Initial supply and approval of changes must comply with the VW 01155 standard.
The chemical safety assessment must comply with the VW 50156 standard.
Material suitability must be in accordance with the VW 91101 standard.
If a fastener with surface protection defined in a specific standard is used and this fastener is coated with lubricant in accordance with the VW TL 52132 standard, the friction coefficients required by the standard defining the surface protection must be observed.
For all fasteners that do not have an additional surface coating or are not defined in the VW 13750 standard and use a lubricating coating in accordance with the VW TL 52132 standard, the coefficients of friction required by the VW 01129 standard apply.
Parts coated with lubricant according to this standard must meet the cleanliness requirements of S01134 of the VW 3 standard, if applicable.
The properties of the products vary and must be tested for the relevant usage situation in terms of the friction coefficients to be achieved. Certain influences such as connection speeds or mating surfaces at threaded joints must be taken into account.
The class indicates water-dispersed synthetic polymers which, after application and drying, give a dry-to-the-touch lubricating film/lubricating film and do not contain hazardous substances. The coating substance must be silicone-free.
Requirements for the lubricant application process:
It must be ensured that no chromic acid, chromic solutions or other acid residues enter the lubricant coating bath. To avoid the risk of condensation, the parts must be packed dry and only after they have reached ambient temperature. The effectiveness of the lubricant coating must be checked in terms of the friction coefficients of the threaded elements in coordination with the receiving plant. If threaded fittings that have previously been coated with lubricant are coated again, this may give different friction coefficients than the initial coating.
Notes on lubricant application process:
The selected process must guarantee reliable and uniform wetting of the surface with the lubricant. Before applying the lubricant, the parts to be coated must be dry and slightly warmed (the object temperature should be approximately 40 degrees to 50 degrees, not exceeding 75 degrees). The temperature of the coating material must not fall below 20 degrees during coating (optimum should be between 25 degrees and 35 degrees, not exceeding 45 degrees).
The coating material is usually supplied as a concentrate. The mixing ratio of the coating material concentrate and preferably demineralized water should be selected in such a way that the desired friction coefficients on the overall layer structure are achieved and maintained.
Bath concentration should be controlled and documented by determining the dry residue or using a refractometer.
The bath pH value should be checked according to the coating material manufacturer's specifications (at least once a day, per shift, taking into account the specified limits).
Coated gear parts are preferably dried in a tunnel system, but a centrifugal system is also possible. Drying should be carried out at a speed and heat applied appropriate to the part spectrum. The exact setting parameters (rotation speed, temperature, filling amount) should be determined and documented by the coating company in cooperation with the coating material manufacturer. The maximum permissible temperature for the coating system, for example a maximum of 90 degrees for passivation processes not containing hexavalent chromium, should be taken into account.
The reason for relubrication may be threaded fittings that cannot be reliably coated. Remachining of improperly lubricated parts that do not reach the friction coefficients required for the relevant use case in accordance with the VW 01129 standard is permissible with a release based on the relevant use case.
The parts to be coated must be free of oil and grease and the solvent must be evaporated before further processing. Cleanliness, avoidance of contaminants, proper wetting and effectiveness of the lubricant coating must also be observed. Preheating and drying are omitted in this procedure.
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