AASHTO Guidelines for Corrosion Protection of Steel Bridges Using Duplex Coating Systems, First Edition (2026), addresses paint systems applied over metallic coatings such as hot-dip galvanizing and thermal spray to extend the service life of steel bridges. An introductory section defines duplex coatings, discusses their drawbacks and limitations, and presents case histories of successful use. Later sections cover the qualification of duplex coating systems and a three-step selection process that weighs viability, installed and life-cycle costs, and constructability. Structural design and fabrication considerations are addressed, including combining hot-dip galvanizing with thermal spray coatings. Further sections describe application of the metallic coating, surface preparation, and application of the paint system, together with repair and maintenance of duplex coatings. The guidelines are intended for bridge owners, engineers, and coating specifiers evaluating corrosion protection options for steel structures.