Alloy K-500 (UNS N05500) is concomitantly a centurial material and the very first precipitation-strengthened nickel-based alloy, then developed in the 1920s by the newly-formed International Nickel Company, or Inco.
Derived from Monel 400 (UNS N04400) that was invented in 1901, Alloy K-500 shares many of the same corrosion and tribological characteristics. Being a pioneer alloy with so-called “stain-less” characteristics, Alloy
K-500 also established itself as the first high-strength oilfield nickel alloy, having survived sour service conditions exceeding the capabilities of the low-alloy steels of the time. From early naval propeller shaft applications to
general cross-industrial uses, Alloy K-500 has always been considered a corrosion-resistant alloy, or CRA. For instance, it has been included in the NACE MR1075 document right from the first 1975 edition.