Thermal expansion of electrolytic chromium

Hidnert, P.

doi:10.6028/jres.026.043

Cited by 13 publications

(7 citation statements)

References 6 publications

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“…Hindent [320] found an average coefficient of expansion of 6.8 Â 10 À6 C À1 for annealed electrolytic hexavalent chromium in the temperature range of 20-100 C. The coefficient of expansion at any temperature t between À75 and þ 650 C was shown to be expressed by the formula a t ¼ (5.88 þ 0.01584t À 0.00001163t 2 ) Â 10 À6 . Within the temperature range À100-700 C, the length of a chromium plate specimen is expressed by the formula L t ¼ L 0a [l þ 5.88t þ 0.00774t 2 À 0.00000388t 3 ) Â 10 À6 ].…”

Section: Coefficient Of Expansionmentioning

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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Section: Coefficient Of Expansionmentioning

confidence: 99%

Electrodeposition of Chromium

Mandich¹,

Snyder²

2010

Modern Electroplating

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“…Hidnert [14] showed that an electrodeposited chromium specimen, on the first heating to 500 0 0, decreased in length and that during the cooling to room temperature it continued to decr ease in length. The net decr ease in length amounted to 1.1 percent.…”

Section: Discussion Of Causes Of Effects Of Chromiummentioning

confidence: 99%

Effect of chromium plating on the endurance limit of steels used in aircraft

Logan¹

1949

J. RES. NATL. BUR. STAN.

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Chromium plating reduced the endurance limits of both normalized and hardened (quenched and tempered) SAE X4130 steels; the reduction was larger for the harden ed steel. The endurance limits for steel of a given hardness decreased with increased plating bath temperatures. Baking of the plated steel, at temperatures up to 350 0 C, reduced the endurance limit; baking at 440 0 C increased the endurance li mit of the p lated steel. However (for hardened steel) baking did not restore the endurance limi t to that of the unplated steel. Damaging effects of chromium on the endurance limits of plated teel are attributed to stresses in the chromium and /or steel, which are increased by low te mperature baking but are relieved in part by baking at 400 0 to 440 0 C.

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“…In these regions the coefficients are, in somo instances, negative. Table 3 gives a comparison of the average coefficients of expansion of the samples of cast and of swaged chromium in the present investigation with the average coefficients of expansion of electrolytic cm'omium obtained by the author [1] in a previous investigation. The average coefficients of expansion of electrolytic chromium for various temperature intervals between 20° and 700° C are within the ranges of the coefficients of expansion for the samples of cast and of swaged chromium.…”

Section: Journal Oj Research Oj the National Bureau Oj Standatds [Vou7mentioning

confidence: 97%

“…The average coefficients of expansion of electrolytic chromium for various temperature intervals between 20° and 700° C are within the ranges of the coefficients of expansion for the samples of cast and of swaged chromium. [6], Chevenard [7], and Hidnert [1].…”

Section: Journal Oj Research Oj the National Bureau Oj Standatds [Vou7mentioning

confidence: 99%

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Thermal expansion of cast and of swaged chromium

Hidnert¹

1941

J. RES. NATL. BUR. STAN.

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Data were obtained on the linear thermal expansion of six samples of chromium (99.2 to 96.3 percent) at various temperatures between -190 0 and + 707 0 C. The expansion curves indicated anomalies at low temperatures. These anomalies were reversible on heating and cooling. The temperature at which anomalous expansion occurs appears to decrease with decrease in the purity of the chromium. Hysteresis was not observed on heating cast or swaged chromium to 300 0 C and cooling to low temperatures. Exceptionally low average coefficients of expansion were found for temperature ranges in or near the anomalous regions. The average coefficients of expansion of the samples of chromium from 20 0 C to various temperatures between 100 0 and 700 0 C lie between 5. 7X 10-6 and 10.3X 10-6 per degree centigrade.

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Thermal expansion of electrolytic chromium

Cited by 13 publications

References 6 publications

Electrodeposition of Chromium

Electrodeposition of Chromium

Effect of chromium plating on the endurance limit of steels used in aircraft

Thermal expansion of cast and of swaged chromium

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