Chromating

Chromating forms a conversion coating of complex chromates. The characteristic layer thickness of the resulting protective coating is no more than 0.01 to 10 micrometers. The chromating process itself is quite complex and involved. In automated applications, for example treating the body shell of an automobile, the part being treated often must pass through ten or more in part repetitive baths. At a minimum, it requires the following steps:

• Solvent cleaning: Grease, oil, and other contaminants are removed from the surface by means of solvents and other chemical processes.

• Intermediate rinse: The solvent and cleaning chemicals are rinsed away with cold or warm water. This step is omitted if only organic solvents were used for cleaning.

• Activation: Use of the activator (for example nitrous or sulphuric acid) yields a crystalline layer whose structure is significantly finer.

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