| 配方类型： |
METALS AND THEIR TREATMENT |
| 配方说明： |
Rhodium |
| 配方组成： |
Because of its whiteness, hardness, high reflectivity and corrosion
resistance, rhodium makes an ideal electroplate for many special
applications. Its most important uses are in the optical, jewelry, and
electrical fields, where its high reflectivity, hardness, and chemical
stability make it particularly desirable. Table 1 compares the
reflectivity of rhodium with that of certain other metals. The only
metals used for reflecting surfaces which have a reflectivity higher
than that of rhodium are freshly polished silver and aluminum which,
however lose their high reflectivity after exposure to the atmosphere and
drop to values lower than shown in the table.
Rhodium is reported to be harder than any of the other metals shown in
Table 1 with the exception of chromium, the reflectivity of which is
much lower than that of rhodium. This makes rhodium very desirable for a
reflecting surface since it combines hardness with high reflectivity and
can |
| 配制方法： |
Two general types of rhodium-plating baths are used in which rhodium is present either as phosphate or as sulfate; a special bath is sometimes used in which the metal is present as a combination of the two salts.
The metal content of the rhodium sulfate or rhodium phosphate bath is usually around 2g. per liter (5 dwt. per gal.). The acid concentration is not very critical and may range from 10 cc. per liter upward for either sulfuric acid or phosphoric acid. Higher acid concentration tends to lower the cathode efficiency slightly.
Representative compositions for rhodium sulfate and phosphate plating baths are given in Table 2. It is important in making up either bath to add the acid to the water before adding the rhodium. If this is not done, the rhodium compound may be partially precipitated by hydrolysis.
the best working temperature is 110 to 125'F. The current density may be 10 to 100 amp. per sq. ft. Insoluble platinum anodes are used and the metal content is replenished by the addition of |
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