(from the symbols of the three chemical elements Cu, Ni, and Al), a high-strength, corrosion-resistant alloy of copper and nickel (4–20 percent) and aluminum (1–4 percent). Two grades of Cunial are produced in the USSR: Cunial A (MNA 13–3), which contains 12–15 percent Ni and 2.3–3.0 percent Al, and Cunial B (MNA 6–1.5), which contains 5.5–6.5 percent Ni and 1.2–2.8 percent Al. The alloys are noted for their high corrosion resistance in air and in fresh or salt water. They are as strong as some of the structural steels. Thus for Cunial A, after solution annealing and age hardening, the following properties are guaranteed: ultimate strength σ_u ≥ 700 meganewtons per m² (70 kilograms-force per mm²) and specific elongation δ ≥ 7 percent. In the cold-worked state, Cunial A has a σ_u of up to 950 meganewtons per m² (95 kilograms-force per mm²) with δ = 2–4 percent. The alloys are used in the manufacture of special-purpose parts that must have both strength and high corrosion resistance.