A novel chrome-free surface pretreatment and primer combined in one-step application for aircraft coating is described. First, a high-solids solvent-borne non-chromate epoxy primer (referred to as CD112) is developed. The formulation of CD112 system is based on epoxy/polyamide chemistry, Adheron's proprietary anti-corrosive pigments, and a tightly packed passivating film made of fillers with different geometric shapes. The protective performance of CD112 has been tested at three independent laboratories and shown to pass a 3000h salt spray resistance, compatible to its chromate counterpart, on both 2024-T3 Clad/Alodine 1000 and 7075-T6 Clad/Alodine 1000 aluminum alloys.Second, a chrome-free acrylic emulsion for surface pretreatment of aluminum alloys is formulated, comprising an ~60nm particle size of acrylic resins, metal-chelating reagents, organofunctional silanes, and non-toxic anti-corrosive pigments. An ~1μm dry film is processed on 2024-T3 Bare Al panel (referred to as 2024-T3 Bare/AFP) and then coated with MIL-PRF-23377 Type I approved chromate-based primer. The electrochemical impedance spectroscopy (EIS) data indicate that 2024-T3 Bare/AFP show about 100 times more resistance than 2024-T3 Bare/Alodine 1200.Third, two in situ phosphatizing reagents (ISPRs) were selected to formulate the in situ phosphatizing coating (ISPC) aerospace primers of MIL-PRF-23377 class N, and to promote the formation of a metal-phosphate layer at the molecular level. The ISPC technique combines a chrome-free surface pre-treatment and primer into a single-step application. The EIS data demonstrate that the ISPC CD112 primer on untreated 2024-T3 Al coupons shows 10-100 times more resistance than the control CD112 primer on 2024-T3 Bare/Alodine 1200. The chemistry of the simultaneous reaction of ISPRs catalyzing the curing of the paint film and forming the metal-phosphate layer at the interface will be illustrated.