The part to be hot-dip tinned is first degreased to remove grease, oil, and solid dirt particles. This can be achieved by a number of methods which include immersion in organic solvents or in alkaline solutions, or electrolytic treatment in alkaline solutions. After careful rinsing the component is pickled in an acid bath to dissolve oxide films on the metal surface and to etch it slightly. The products of this treatment are rinsed off and the part is then fluxed to assist the wetting of the surface by molten tin. The basis of many hot-tinning fluxes is aqueous zinc chloride, which is occasionally mixed with ammonium chloride. The prepared part is lowered carefully for a few seconds, into a bath of molten tin held at 250 to 320'C, or for a longer time in the case of large parts, to achieve tinning. As an alternative to dipping-for example, when a coating is required on one face only, the tin is sometimes applied by wiping molten tin over the prepared surface. Large parts are manipulated while the coating
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