Classified under a single 10-digit line (3810100000), these chemical preparations serve two distinct functions: removing oxide scale and corrosion from metal surfaces before finishing, and acting as metal-bearing powders or pastes that facilitate soldering, brazing, or welding joints. Mexico leads US import supply, followed by Japan and Canada, reflecting deep integration with North American manufacturing and the strong Japanese presence in precision electronics assembly materials. Importers should confirm whether a specific formulation is classified here or under a flux-based heading, as the distinction turns on whether the active ingredient is a metal constituent versus an auxiliary chemical agent.

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