Sunday, August 17, 2008

Inorganic Cleaner

The inorganic soils, which include rust and tarnish, solid particle dirt, scale, smut, and cleaning residues, are usually removed by alkaline degreasing or an acid pickle. Rust and tarnish, being insoluble be alkaline degreasing or an acidic or alkaline chelating solutions, with or without electric current. Water insoluble solid particle often adhere to oil present on the surface and are therefore removed simultaneously with the oil. Smuts which result from pickling are very troublesome and should be avoided. Inorganic cleaning residues may be films of oxides, phosphates, silicates, and the like remaining on the metal surface after alkaline cleaning and not removed by the rinse and mild acid dips that follows. Care in rinsing is the best way to eliminate trouble from this source.

Not all plating operations require the same degree of cleanliness of the basis metal. It is possible to plate from an alkaline cyanide plating solution articles that are dirty compared to those that may be processed in acid plating baths such as nickel. Therefore, a much shorter cleaning cycle may be employed for alkaline cyanide plating. It is poor practice, however, to contaminate a plating solution by using it as a combination cleaning and plating bath.

Lyon stated that an absolutely chemical clean surface is not required for production of an acceptable electroplate. By definition, a chemically clean surface is one that has no film on it that might be detected by chemical or physical test, obviously such a surface can be realize only with extreme difficulty even in the laboratory. It is generally agreed, however, that surfaces substantially free of grease, oil and gross oxide films are needed for the best electroplates. Therefore it is standard practice to clean as thoroughly as is economically feasible. Shop tests for the presence of hydrophobic soils have been studied by Linford and Saubestre. The one most commonly applied is the water-break test. Parts that pass this test are assumed to be sufficiently clean been demonstrated, the atomizer test described by Linford and Saubestre should be used. This test is about 10 times as sensitive as the water-break.

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