Ferrous and nonferrous metals were other significant export products. Gauge differs between ferrous (iron-based) metals and nonferrous metals such as aluminum or copper. It serves clients in the metals industry, both the ferrous and the nonferrous metals sector. Many industries use GTAW for welding thin workpieces, especially nonferrous metals. The tin-plating process is used extensively to protect both ferrous and nonferrous surfaces. Numerous nonferrous alloys, cast irons, powder-metallurgy and plastics are used in the manufacture of gears. Deposits of nonferrous metals were limited or nonexistent. The Soviet Union exported timber, nonferrous metals, rare-earth metals, and fuel to Japan. Sichuan and Longxi County, Gansu has clusters of mining firms for nonferrous metals. These tools are mostly used for the machining of nonmetallic and nonferrous materials. Ridder is a center of mining operations and processing of nonferrous metals. The Caucasus also possessed plentiful coal and peat, as well as nonferrous and rare metals. Of the 800,000 tons of nonferrous metals shipped, about 350,000 tons were aluminium. Nonferrous alloys contain no appreciable amounts of iron. TSP is used as an ingredient in fluxes designed to deoxygenate nonferrous metals for casting.