Gunmetal
Why gunmetal is over brass and how you keep the two apart on the dash.
gunmetal is the German trade name for copper-tin-zinc cast. Rg5 is called CuSn5Zn5Pb5, Rg7 has more tin and more lead. Both are sand casting alloys and therefore carry a rough cast skin, visible cast seams and often still core sand in the cavity — features that never have a pressed or turned brass part.
The price is the tin. Foundries buy red-cast scrap as remelting material, because it becomes red-cast again, not copper. What they pay depends on how reliable the composition is: a post in which brass floats, lifts the zinc content and lowers the tin content, and that's exactly what a foundry doesn't want to have to guess.
Since the materials for drinking water are evaluated and listed, two generations have been placed side by side in the scrap: classic lead-containing gunmetal and newer, lead-free fittings, which are often alloyed with silicon. They don't let the eye separate. In practice, origin and year of construction therefore say more than the colour — everything from heating, drinking water and pump technology before the turn of the millennium is with high probability the classic gunmetal.
Why is gunmetal above brass?
At the alloy: Gunmetal like Rg5 (CuSn5Zn5Pb5) contains around 85 percent copper and about five percent tin. Brass comes out with 58 to 63 percent copper, the rest is the cheaper zinc. Tin is the most expensive of the metals involved in the London Metal Exchange — copper and tin are driving the red-cast price together. That's why separating from brass is worth it.
How do I distinguish cast red from brass?
At the color of a fresh wedge or interface: gunmetal looks reddish to salmon, brass yellow. At the shape: Gunmetal is cast material — valve body, pump housing, water meter, often with rough casting skin and cast seam, while brass is usually pressed, turned or available as sheet metal. Gunmetal sounds duller, and the fracture surface is grainy instead of tough.
Which parts on gunmetal fittings press the price?
Everything that weighs, without being non-ferrous metal: spindles and springs made of steel, stainless steel sieves, ceramic cartridges, plastic handles, rubber seals, glass and counters in water meters, with residual water in closed housings. Chrome-plated surfaces are uncritical, the layer is thin. Pliers and pipe keys get out most of it in a few minutes.
Is it worth a few gunmetal parts, or should I collect?
Both go. Gunmetal is dense: a bucket of valves and fittings weighs more than it looks, and is usually above the minimum payment of 25 euros. From the Rhine-Neckar area you can get small quantities without appointment in Ludwigshafen In the case of the For shipping it is worth collecting: Each package costs 6 euros, and from the scale limit we pay more.
Do you buy bronze like plain bearings or ship screws as gunmetal?
Tin bronze and gunmetal are closely related, both are copper-tin alloys; in our list is the type gunmetal, there you enter bronze parts when selling. The important thing is the separation of composite parts: plain bearing shells with steel back and bushings, which are still sitting in the steel housing, are not pure non-ferrous metal. It is calculated according to the actual grade.
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