Dissimilar Metal Compatibility Matrix

Dissimilar metal compatibility matrix — required protective treatment level (1–9, where 1=maximum protection required and 9=minimal or no protection needed) for each pair of metal groups (A–T, anodic to noble) per MIL-STD-889C Table I. Covers three service environments: seawater, marine atmosphere, and industrial atmosphere. Also flags same-metal diagonal entries. Used to determine dissimilar metal joint protection requirements in aerospace, marine, and industrial structures. Complement table: Surface Treatment Specs (dissimilar_metal_protection_* PKs) lists the specific protective treatments corresponding to each protection level.