The “ Porsche PN 11011 Surface protection for metal parts - Basic information and overview” standard, developed by the Volkswagen automotive company, has replaced the PN 11003-1 standard. The European Union end-of-life vehicle directive 2000/53/EC prohibits the use of hexavalent chromium (Cr(VI)) as a corrosion protection agent. This necessitates a change in surface protection systems.
All surfaces must meet the requirements of the PN 1004 standard for contaminant prevention. Previous types of surface protection containing Cr(VI) are no longer valid. The structure and organization of the standard are retained. The abbreviation surface protection indicates a specific corrosion protection level and coating color.
The Porsche PN 11011 standard applies to the general surface protection of metal vehicle components by applying metallic and non-metallic coatings. If the functionality of a part directly depends on surface protection, additional information may be added. For example, specific surface protection systems for brake lines, wheels, and body paint are specified in the standards and delivery specifications. These are listed in the standard's appendix (Appendix B).
Surface protection is indicated by abbreviations in drawings and technical documentation, along with the number of this standard. This identifies a specific coating with associated properties such as corrosion resistance and finish. The structure of the four-digit abbreviation is illustrated in the figure provided in the standard. The first digit identifies the process. The second digit identifies the resistance class (process and resistance types are listed in the tables provided in the standard). The third and fourth digits distinguish characteristics within a surface protection process, such as design, appearance, and finish, and the corresponding resistance class.
Surface protection treatments are divided into resistance classes as follows:
Different surface protection treatments with the same resistance class may result in different corrosion protection and functional properties.
In the surface protection selection process, it is important to distinguish between the specified protection types and those available on the market.
The selection of the specified surface protection depends on the mounting position, the type of corrosion stress, and the specific requirements of the operating parts. These protection types, along with their abbreviations and requirements, are summarized in the table titled "Protection Class, Abbreviations, and Requirements" provided in the standard. Thick-frame protection types are preferred for standard parts.
For some parts, it is neither possible nor necessary to specify the surface protection. In these cases, it is sufficient to specify the process code letter followed by the digits 010 according to the table titled "Commercially available protection types" provided in the standard (e.g., c010 = galvanized).
The values specified in the tables are minimum coating thicknesses. During coating, the manufacturer must ensure that the finished dimensions of the parts are within the allowable tolerances. If, in justified cases, specific coating thicknesses cannot be exceeded, the maximum allowable coating thickness must be specified on the drawing.
Coating processes used to apply zinc flake coatings to bulk material parts often require compromises in coating thickness uniformity. Even if a uniform, dimensionally stable coating thickness is achieved across most of the surface, material buildup exceeding the specified tolerance limits can occur, particularly at the tooth root and on contact surfaces (e.g., under the screw head). However, this does not mean that the parts are unusable. In such cases, the dimensional accuracy of coated threaded parts can no longer be determined using measuring instruments, but only through individual measurements. Therefore, when testing using a ring gauge, dimensional accuracy is still considered to be achieved if the ring gauge can be screwed in with the maximum tightening torque.
Unless otherwise agreed, for threaded parts that have been finished or finished to increase fatigue strength, a coating process with a baking temperature not exceeding 220°C should be selected. This restriction also applies to case-hardened threaded parts. Otherwise, a noticeable reduction in the threaded part's fatigue strength can be expected.
Generally, only certain types of surface protection and lubricant-free electrocoated surfaces are suitable for bonding, overcoating and sealing.
Threaded mechanical fasteners require lubrication according to standards PTL 7540 or VDA 235-101. The total coefficient of friction should be in the range of 0,09 to 0,14. The effect of lubricants on the effectiveness of adhesive coatings (e.g., microencapsulation) for fastening or sealing purposes should be considered.
Only certain types of surface protection are electrically conductive. All other types of seals are insulating. Zinc flake coatings are not suitable for electrical connections. Internal resistance increases due to oxidation of the zinc flakes under corrosion stress.
In short, the Porsche PN 11011 standard is an internal specification that details the requirements for surface protection of metal components used in Porsche vehicles. It outlines various coating systems and their applications, ensuring corrosion resistance and compliance with environmental standards. This standard provides a comprehensive overview of surface protection methods for metal parts, referencing other standards for specific coating systems and application areas.
This standard covers various coating systems, such as zinc-iron and zinc-nickel coatings, with specifications regarding thickness, passivation, and sealing processes.
Additionally, this standard emphasizes the use of coatings that are free of hexavalent chromium (Cr(VI)) and comply with the restriction of hazardous substances (RoHS) directive, and is compliant with environmental and safety regulations.
Essentially, this standard specifies performance criteria for corrosion resistance. For example, certain zinc flake coating systems are designed to withstand salt spray testing for up to 480 hours without red rust, depending on the specific coating and application.
In summary, the PN 11011 standard serves as a guide for suppliers and manufacturers to ensure that metal components meet Porsche's quality and durability standards through appropriate surface treatments.
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