Posted by John Swensen on February 20, 2002 at 14:13:50:
In Reply to: so, is red brass unsusceptable posted by Ian Easton on February 20, 2002 at 08:16:49:
There seems to be a universal consensus amoung metalurgists that high-copper brasses (>= 85% copper; eg: red brass, gilding brass, etc.) and the nickel silvers (12-18% nickel in the brass) are immune from dezincification (red rot).
Standard cartridge brass (70% copper, 30% zinc) was developed for gun cartridges, which are formed by deep drawing (stretching a flat disk into a narrow tube), and it is generally considered to be the most formable brass, making it the easiest to turn into tuba-like shapes. For the high-volume manufacturers, the machines can be run faster, with fewer annealing steps, and with fewer rejected parts. For the low-volume manufacturer, the widespread use of cartridge brass means there will be many suppliers, and prices will tend to be lower than for less commonly-used alloys (like, say, red brass). Also, cartridge brass is readily available in seamless tubing in a variety of sizes, but red brass or nickel silver tubes would require special orders, with (presumably large) minimum quantities. For both ends of the mass-production scale, processes designed around cartridge brass will need to be adjusted to handle metals with different forming characteristics. Just because they are different from the mainstream alloys, red brasses and nickel silvers will cost the manufacturers more to transform them from raw stock to finished instruments.
I did a quick search for copper alloy prices and discovered that cartridge brass cost $5.50/pound, copper cost $6.00/pound, and nickel silver cost $8.75/pound in the same quantities and sizes. If this survey is representative of industry-wide pricing, the price differences among any alpha brasses (brasses with < 40% zinc) are negligible from the standpoint of raw metal costs, but nickel silver is about half, again, as expensive as cartridge brass. This may not matter much, because (ignoring the weight of the valves) a 25-pound tuba only represents $137.50 worth of cartridge brass, or $218.75 worth of nickel silver, a difference of only $81.25.
Red brass leadpipes are common (my B&S has one), and nickel silver slide tubes are very common (many high-end tubas use them, and look at any lacquered Bach trumpet). Personally, I would prefer a nickel silver leadpipe, nickel-silver slides (including the bow), with brass outer-slide tubes, but not enough to special-order a horn built that way, and I would choose a better-sounding horn over a worse-sounding horn that had a potentially longer lifetime before requiring a new leadpipe or one or two new slides.
So why are nickel silver and red brass not universally used for slides and leadpipes? They cost a little more to make, and not enough buyers care about long-term corrosion to warrant the higher manufacturing cost. After all, if we were all that concerned about corrosion, we would snake out and rinse our leadpipes and slides every day, and who does that?