ASTM B555-86(2023) PDF

Overview

ASTM B555-86(2023), Standard Guide for Measurement of Electrodeposited Metallic Coating Thicknesses by Dropping Test, provides a guidance framework for evaluating the thickness of electrodeposited metallic coatings using the dropping test method. Developed by ASTM International, this guide is widely referenced in quality assurance processes where the thickness of coatings like zinc, cadmium, copper, and tin is essential to product performance but ultra-precise measurement is not required.

The dropping test method offers an approximate measurement by applying a corrosive solution to the coated surface and timing its penetration to the substrate. While this approach is less accurate than other methods, it is useful for quick or preliminary assessments on metallic surfaces.

Key Topics

• Purpose and Use

  • Ensures that metallic coatings meet minimum thickness requirements for durability, corrosion resistance, and performance.
  • Useful when moderate accuracy is sufficient and rapid results are needed.

• Suitable for Specific Metals

  • Intended for zinc, cadmium, copper, and tin electrodeposited coatings.
  • Not generally recommended for alloy coatings or coatings with significant impurities.

• Method Description

  • A controlled flow of corrosive reagent is applied dropwise onto the inclined coated surface.
  • The elapsed time until the substrate is exposed is measured.
  • The coating thickness is estimated by multiplying the time by a thickness factor.

• Influencing Variables

  • Cleanliness of the test surface
  • Consistency and concentration of the test solution
  • Dropping rate and drop size
  • Test temperature and solution drainage
  • Presence of alloy layers or impurities

• Limitations

  • Not as reliable or convenient as more advanced methods (e.g., magnetic, X-ray, coulometric).
  • Operator judgment and strict test condition control are necessary for acceptable repeatability.

Applications

• Quality Control in Electroplating

  • Provides a quick method for confirming that protective coatings meet minimal specifications in manufacturing and finishing lines.
  • Especially useful in environments where high-volume inspection is required but ultra-precise measurements are not critical.

• Field Assessments

  • Can be employed for on-site evaluation of coating thicknesses without the need for specialized laboratory equipment.

• Preliminary Testing

  • Suitable as a screening method before more precise testing with devices such as coating thickness gauges.

• Industry Sectors

  • Used in automotive, aerospace, electronics, and hardware manufacturing where surface protection is vital.

Related Standards

• ASTM B487: Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of Cross Section.
• ASTM B499: Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis Metals.
• ASTM B504: Test Method for Measurement of Thickness of Metallic Coatings by the Coulometric Method.
• ASTM B568: Test Method for Measurement of Coating Thickness by X-Ray Spectrometry.
• ASTM D1193: Specification for Reagent Water.

Practical Value

The ASTM B555 dropping test is an efficient way to estimate metallic coating thickness where rapid, on-site, or non-laboratory evaluation meets project needs. While best for approximate thicknesses, it helps manufacturers and inspectors ensure coatings satisfy essential performance and protection functions. For strict accuracy and reliability requirements, more advanced ASTM methods should be considered.

Using established international principles, ASTM B555 supports consistency in test practices across industries and helps minimize technical barriers to trade through global standardization in coating thickness measurement.

Keywords: ASTM B555, dropping test, electrodeposited coating thickness, metallic coatings, zinc coating, cadmium coating, copper coating, tin coating, quality control, coating measurement methods.