ELECTROPLATING

Problem Solving

Electroplating

The following examples illustrate some of our contributions to this business sector:

• Touchstone was asked to investigate the cause of poor surface appearance of a nickel plated steel stamping. It was found that the flecks were nearly perfect circles on the electroplate surface and the plating was not as thick as that on the balance of the steel surface. A literature search found that this plating defect is caused by gas bubbles, which can form on the surface during plating.
• Touchstone performed an investigation to determine the nature and cause of surface damage which had developed at various locations on a hard-chromium plated, surface hardened steel roll. The findings of this investigation indicated that the surface condition was most probably due to use conditions. The hard chromium surface was found to be within the specified limits for hardness, particularly in the damaged area as indicated by microhardness determinations.
• Sections from two hard-chrome plated leveler rolls were examined to determine the cause of heavy, uneven surface wear. The chemistry of the steel was checked, along with the microstructure, hardness profile, and thickness and hardness of the chrome plating. All were within specifications except the plating thickness on one roll. This roll had a very thin plating on it, 0.17 mil (0.5 mil was required) where the other rolls had a plating thicknesses of 0.55 mil+. The damage was believed to be the result of use conditions rather than metallurgical problems.
• A frequent problem encountered with plated steel rolls is non-plated areas on the surface. Evaluation of several specimens found that the defects were areas where non-metallic inclusions in the original forging existed. Nonmetallic areas usually will not plate in standard plating baths. The problem is the result of using steel forgings which are not of sufficient quality to allow consistently good plating.
• Knoop microhardness measurements were performed on three different chromium-plate thicknesses to determine whether hardness was related to plating thickness. Similar hardness values resulted regardless of plating thickness.
• Touchstone has performed numerous investigations in electro-galvanized steel, evaluating adhesion problems, conversion coatings, plating bath problems, formability, iron-zinc layer characteristics and many others.
• A number of fractures screws were examined for the manufacturer of steel grating to determine the reasons for failure. These screws were used to hold down aluminum safety edging used on steel stairs. The screws had failed at various locations through-out the country, but had been purchased as a single lot. SEM, metallographic and Rockwell Hardness measurements were used to determine that the screws failed due to hydrogen embrittlement. The most likely source of the hydrogen was found to be the electrolytic cadmium plating process.
• A supplier of reconditioned heat exchangers needed to design an environmentally acceptable way to deal with plating waste. The waste was treated by a modification of the process used to remove metals from pickling waste like those generated by steel mills. The recovered sediment was sold to a smelter and the effluent was found to be cleaner than the potable water used to supply the business.
• Several anodized specimens were evaluated using AUGER Electron Spectroscopy (AES) to determine what differences existed between anodized sheet and stock, untreated aluminum sheet. The results demonstrated that SiO2 was present on aluminum sheet after anodizing. This represented the only significant difference seen after anodizing.

The above examples are only a sample of our work in this area. We would be pleased to provide any additional information you may require. We also invite you to review examples on our website of work that we have performed in support of other business sectors.