If the zinc alloy castings are manufactured properly, they are exceptionally durable. And the number of instances of zinc pest is minuscule in comparison to the overall production of zinc castings in our hobby from Asian production.
The problem in China is quality control involving small subcontractors for certain parts such as trucks, couplers and frames. Some of these model-train subcontractors operate out of garage-sized facilities that are far from state of the art. Some, not all, of these proprietors are either sloppy or indifferent in the production process for these castings.
The low-volume nature of these parts productions is what prompts the primary contractor to seek outside help.
Part of the answer would be for China to inspect and regulate small contractors. I suspect that’s not a government priority right now.
Also, for those who continually assail China for its quality production, I again have to point out that the zinc pest problem was also prevalent in toy and model train production in the prewar and postwar eras. Lionel’s 700E Hudson also suffered from zinc pest more than 80 years ago.
American manufacturers had to learn how to properly produce zinc castings, religiously avoiding impurities and performing best-practice standards. They eventually succeeded. China can, too, if it wants.
As for other options, well, ... . Let’s just say zinc alloys are used in so many products, usually of high quality, that I feel comfortable saying manufacturers rely on it as more useful than other choices. It’s their business, and I’m sure they have considered all the options.
