Hyundai Kia MS611-15 Electroplating Zinc and Zinc Alloy Coating and Trivalent Chromate

Developed by Hyundai-Kia Motors, the oldest motor vehicle manufacturer in Korea, the “ Hyundai Kia MS611-15 Electroplating zinc and zinc alloy coating and trivalent chromate” standard describes the requirements and test methods for electroplating zinc and zinc alloy coating and trivalent chromate materials used for corrosion protection in automotive steel parts. For coating brake hose fittings, the “MS611-16 Zinc-based electroplating for brake hose fittings” standard is deemed appropriate.

The classification, notation and thickness of the coating are given in the table in the standard on the following basis:

• Copper or copper alloy base
• Iron or iron alloy base

Chromate treatment is not required for parts painted with electroplating coating after zinc and zinc alloy coating. However, e-coated parts are etched instead of chromated.

The dark zinc nickel alloy coating of bolts and nuts shall meet the torque coefficient requirements given in the “MS611-14 Torque coefficient of hardware” standard by applying organic inorganic finishing (top coating) after chromate treatment.

Finishing using resin type material should not be applied to parts where the coating solution is expected to accumulate in the grooves and to which electric current is applied, including zinc-nickel alloy coated (black) ground and cross-grooved connecting bolts, screws, eye bolts and plugs.

In terms of general requirements, the coating should have a uniform fine particle appearance and be free from bubbles, open bases or other defects that could affect the appearance or protective value of the coating. However, chromating may cause slight mixing or color variation.

The detailed requirements in this standard are described as follows:

• The coating thickness shall be in accordance with the table given in the standard (based on copper or copper alloy base and iron or iron alloy base). E-coating means the minimum coating thickness excluding the chromate coating layer. The coating thickness target area of ​​bolt and nut shall be in accordance with the figure in the standard (excluding the ridge and groove).
• The coating composition, nickel content of zinc nickel alloy coating shall be in accordance with the table given in the standard. The target area of ​​bolt and nut hardware shall be in accordance with the figure in the standard (excluding ridge and groove).
• Corrosion resistance, when salt spray testing is performed in accordance with this standard, there shall be no white corrosion or red rust in the target area after testing for the time specified in the table given in the standard. The target area of ​​bolt and nut hardware shall conform to the shape in the standard (excluding the ridge and groove).
• Water resistance, in the case of e-coating, shall be free of blistering, cracking, discoloration, softening or loss of adhesion after being subjected to water resistance testing for 240 hours according to this standard (excluding the back and groove).
• Hydrogen embrittlement removal:
  • For bolts with a tensile strength greater than 10T and spring washers, hose clamps, and pins with a Rockwell hardness scale greater than 35, hydrogen embrittlement removal must be carried out within 3 hours after coating.
  • If the parts need hydrogen embrittlement removal and chromate treatment, chromate treatment should be performed after hydrogen embrittlement removal and then activation treatment should be performed.
  • Before the chromate process, it should be baked at 200 degrees plus/minus 10 degrees and for more than 3 hours to remove hydrogen embrittlement.
• Every material must meet the MS201-02 standard regarding heavy metals and harmful substances.

In this standard, test methods are defined as follows:

• Pre-treatment: the sample is used for testing and analysis as it is. Only if there is dust, dirt or other foreign matter on the surface, the surface is cleaned using distilled water.
• Thickness test: This test is performed according to the microscopic method in accordance with the following standards:
  • “KS D 0246 Thickness test methods for metallic coatings”
  • “ISO 1463 Metallic and oxide coatings - Measurement of coating thickness - Microscopic method”

Or it is done according to the X-ray spectrometric method in accordance with the following standards:

• “KS D 0246 Thickness test methods for metallic coatings”
• “ISO 3497 Metallic coatings - Measurement of coating thickness - X-ray spectrometric methods”

• Salt spray test: This test must comply with the following standards:
  • “KS D 9502 Neutral, acetic acid and copper accelerated acetic acid salt spray tests”
  • “ISO 9227 Corrosion tests in artificial atmospheres - Salt spray tests”

The test piece should be allowed to sit for at least 24 hours after chromate treatment before testing.

• Water resistance test: This test should be in accordance with the standard “MS600-35 Test methods - Paint and coating film for bodywork”. The test temperature should be 40 degrees plus/minus 2 degrees.

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