Corrosion-resistant nickel alloys are vital to the chemical process industry. They are known
to be significantly more resistant than stainless steels to key chemicals such as
hydrochloric and sulfuric acids. Even though the Ni-Cr-Mo alloys possess an excellent
corrosion performance, there has always been a need for materials with improved
resistance to these two mineral acids without the drawbacks of the Ni-Mo materials. These
drawbacks are mainly related to their intolerance to dissolved oxygen and oxidizing
chemicals, and these Ni-Mo alloys are much less stable metallurgically than the Ni-Cr-Mo
alloys. To fill in this gap, a new Ni-Mo-Cr alloy was recently developed and commercialized.
This paper will provide new comparative corrosion data between the new alloy and several
Ni-Cr-Mo and Ni-Mo materials in a variety of environments, mainly in hydrochloric and
sulfuric acids, with a special emphasis on the effects of oxidizing chemicals in the acids.
Key words: New Ni-Mo-Cr alloy, Ni-Cr-Mo, Ni-Mo, iso-corrosion diagrams, hydrochloric
acid, sulfuric acid, dissolved oxygen, ferric ions, and cupric ions