Caution: Some of the methods
used involve caustic or poisonous liquids and fumes that may permeate an
entire house. Plastic gloves and adequate ventilation are mandatory. The
work area and you should be well protected from possible damage or
contact.
Often used industrially, immersion of components in liquids can solve some otherwise difficult problems in coating. Frequently the application of an external coat presents an undesirable effect or method to the extent where it is unsatisfactory or impractical. Very often this is associated with metallic parts from brake rods to frames and shells.
Hand or spray painting a large number of parts is tedious and time consuming. Commonly, for more rapid production , industry resorts to batch dipping, including partial. Consistency of medium should be thin enough to avoid thick layering, but still provide adherence and coverage. Often those used for spraying are close. Hand shaking or tapping on container side will help remove excess. Attachment to a vibrator can speed draining. Whirling can be messy.
Too often metals are not amenable to coating because of their smooth surface properties. Preparation by abrasive or chemical etching helps, but often is impractical. Frequently metal parts comprise movable joins which can not tolerate extra coating dimensions or where lubricants may remove coatings. Many chemicals react with metals to BLACKEN _ or form various colored, surface finishes with almost zero thickness. Brushing is an expedient method of application, but often streaks occur, recesses and cavities are not covered and colors are not even. Due to evaporation, required shade may not be attained because of insufficient contact time. With properly prepared items, immersion in chemical solutions can solve these problems. Stirring, brushing or other agitation speeds the process by circulating liquid and eliminating air bubbles from cavities. Vibrators or, better, sonic cleaners are a boon. Although black or rust are more common, gun blue or antiquing solutions can produce additional effective colors. Various shades can be produced by controlling the time or dilution and temperature.
Often loco rods and valve gear have brass. aluminum or zamac parts, which do not remotely resemble steel. Plating can produce a closer approximation. Basically the process consists of a migration of dissolved metallic ions to the immersed object's surface, where they react to bond a very thin metallic coating. Coating thickness is controlled by time, solution concentration and temperature. Electro-plating or electrolysis adds a current loop from an external DC supply to speed and further control the process. The internal solution current migrates ions, usually dissolved from the input electrode , to the output object (electrode), where they are deposited. Dry cells make good power supplies. Many kits are marketed, including some that permit brushing for uneven effects.
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