Zinc plating defects pdf

Plating layers are thin and reflective, and typical defects that occur are microscopic and three-dimensional. Inspections using conventional measuring instruments or 2D images have various problems when it comes to ensuring reliable plating quality. Commercial zinc plating is accomplished by a number of distinctively different systems: cyanide baths, alkaline noncyanide baths, and acid chloride baths. This article focuses on the composition, advantages, disadvantages, operating parameters, and applications of each of the baths. It provides information on the control of thicknesses of zinc COATING REQUIREMENTS 4.1 Finish and Appearance 4.1.1 Over the significant surface, the plated article shall be free from clearly visible plating defects such as blisters, pits, roughness, nodules, cracks, burning or unplated areas : d shall not be stained or discoloured. • Defects include: 1. Surface Shrinks 3. Solidification cracking 2. Laking or Waving 4. Hot tears 36. Surface Shrinkage • Usually coincides with hot surface spots on die. • Caused by delayed solidification in this area compared to surrounding areas, hence increased contraction. Zinc Plating Acid Cleaning Caustic Cleaning Solvent Degreasing Work Practices Personal Protective Equipment Hygiene Procedures Monitoring CONCLUSIONS AND RECOMMENDATIONS REFERENCES APPENDIX A. Sampling Results iv iii ix 1 3 3 4 4 6 11 11 16 18 20 26 26 30 32 32 32 58 58 62 65 67 70 73 80 82 84 87 88 88 90 92 97 . LIST OF TABLES Consequently, an objectionable defect is larger than 100 μm. When viewed under an optical microscope at high magnifications, such a defect can extend to more than one view field. Based on their origin, the surface defects encountered in galvanized and galvannealed sheet products can be broadly classified into six categories [5]. 1. 6.0.5 Fingerprints: No fingerprints, whether they p enetrate the plating or not, are allowed in Class A, B or C. (Wear appropriate protective garments) 6.1 Defect Definitions: 6.1.1 Rainbow effect - Zinc plating may have discoloration or the "rainbow" effect. 6.1.2 Rust/ Oxidation - Chemical reaction of exposed metal with oxygen (air). The plating tanks typically are equipped with some type of heat exchanger. Mechanical agitators or compressed air supplied through pipes on the tank bottom provide uniformity of bath temperature and composition. Chromium electroplating requires constant control of the plating bath temperature, current density, plating time, and bath composition. ASTM specifications are among the most common standards used for Zinc and Zinc-Nickel plating. ASTM B633 is a widely used standard for Zinc and ASTM B841 for Zinc-Nickel. Parts should be free of defects prior to plating to ensure the highest quality coating. 6.1 The coatings shall be non-alloyed zinc produced by electrodeposition. 6.2 Defects in the surface of the basis metal, such as scratches, porosity, pits, inclusions, cracks, roll marks, and die marks, may adversely affect the appearance and performance of coatings applied thereto despite the observance of the best electroplating practices. This paper is intended for guidance to the practical plater for preventing and curing the most commonly encountered troubles in plating solutions. It is not intended to be exhaustive, nor is it written from an academic point of view. This supply specification covers Zinc Plating with Trivalent Chrome Passivation 2.3 The component's with cracks or other serve material defects are