Protective Value of Chromium-Plate

Baker, Edwin M.; Pinner, W. L.

doi:10.4271/280024

Cited by 3 publications

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“…The random directions and spacings of Type M cracks in chromium indicate that these occur when isotropic internal stresses exceed the tensile strength of the deposit. Although cracking similar to Type Y has been observed previously in chromium deposits up to 0.050 mil thick (1,2,11,(24)(25)(26), it appears thai no serious attempt has ever been made to explain their origin other than by vague attributions to "stress." In the absence of externally applied stresses, anisotropic stress distribution in the deposit appears to be the most likely explanation of the directionality of Type Y cracking.…”

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confidence: 81%

Effect of Surface Preparation on Cracking and Structure of Chromium Deposits

Hardesty

1964

J. Electrochem. Soc.

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Conventional bright chromium deposits (0.02-0.05 rail thick) on buffed nickel plates often develop a directionally oriented crack pattern which may adversely affect appearance and corrosion resistance. This cracking was found to occur by interaction of polishing-induced, directional residual stress in a surface layer of the nickel with isotropic internal stress of the chromium deposit. Removal of the stress-containing layer by electropolishing or stress relief by annealing eliminates this cracking. Similar cracking can occur in bright nickel-chromium composites plated on polished steel. Chromium deposits on electropolished nickel are apparently strongly epitaxial. Observed variations in appearance, porosity, and corrosion behavior of deposits on individual grains of wrought nickel correspond to similar variations symmetrically distributed in chromium plated on spherical nickel single crystal. The significance of these observations is discussed.The use, efficacy, and electrochemistry of microcracked chromium in controlling corrosion of copper-nickel-chromium plated coatings for decorative automobile trim have been discussed by a number of authors (1-6). This type of cracking [Type M in Lindsay's (2) classification] is described by Lovell (1) as "... a fine network of cracks extending through the chromium and invisible to the unaided

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confidence: 81%

Effect of Surface Preparation on Cracking and Structure of Chromium Deposits

Hardesty

1964

J. Electrochem. Soc.

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“…Baker and Pinner [237] used this test to study the porosity and cracking of decorative chromium coatings. An important precaution is to apply it only to articles completely covered with chromium or to insulate all areas not chromium plated.…”

Section: Porosity and Crackingmentioning

confidence: 99%

“…Until about 1960 decorative chromium deposits were generally confined to thicknesses of 0.5 mm or less since macrocracking would begin at this thickness. Under normal service conditions, macrocracks in thick deposits would contribute to a reduction in corrosion resistance [237]. Since the development of bright macrocrack-free chromium plating [242,243], it has been demonstrated that if the undercoating of nickel or copper and nickel is of adequate thickness (generally more than 25 mm), a thicker decorative chromium plate adds substantially to the corrosion resistance.…”

Section: Corrosion Resistancementioning

confidence: 99%

Electrodeposition of Chromium

Mandich¹,

Snyder²

2010

Modern Electroplating

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Electroplated chromium deposits rank among the most important plated metals and are used almost exclusively as the final deposit on parts. Without the physical properties offered by electroplated chromium deposits, the service life of most parts would be much shorter due to wear, corrosion, and the like. Parts would have to be replaced or repaired more frequently, or they would have to be made from more expensive materials, thus wasting valuable resources.The thickness of electroplated chromium deposits falls into two classifications: decorative and functional. Decorative deposits are usually under 0.80 mm in thickness. They offer a pleasing, reflective appearance while also providing corrosion resistance, lubricity, and durability. Decorative chromium deposits are typically plated over nickel but are occasionally plated directly over the substrate of the part.Functional ''hard chrome'' deposits have a thickness customarily greater than 0.80 mm and are used for industrial, not decorative, applications. In contrast to decorative deposits, functional chromium is usually plated directly on the substrate and only occasionally over other electrodeposits, such as nickel. Industrial coatings take advantage of the special properties of chromium, including resistance to heat, hardness, wear, corrosion, and erosion, and a low coefficient of friction. Even though it has nothing to do with performance, many users want their functional chromium deposits also to be decorative in appearance. Functional deposits are also used on parts such as cutting tools and strip steel and are even thinner than decorative deposits.The most common and oldest commercial type of chromium process utilizes hexavalent chromium (Cr 6 þ ) in an aqueous solution containing one or more catalysts. The

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The Durable CASS Test

Hardesty

1973

SAE Technical Paper Series

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Protective Value of Chromium-Plate

Cited by 3 publications

References 0 publications

Effect of Surface Preparation on Cracking and Structure of Chromium Deposits

Effect of Surface Preparation on Cracking and Structure of Chromium Deposits

Electrodeposition of Chromium

The Durable CASS Test

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