Under the national "Dual Carbon" goals， an environmentally friendly， coating-free， high-strength， and high-corrosion-resistant highway guardrail steel， LG500EW， has been developed. This addresses issues with traditional galvanized plain carbon steel Q235， such as low strength， poor corrosion resistance， and significant environmental pollution caused by galvanizing processes， thereby improving the safety and service life of highway guardrails while reducing carbon emissions across the entire industry chain. LG500EW employs a alloy design of low carbon， high chromium， and trace amounts of copper and nickel， combined with Thermo-Mechanical Control Process （TMCP） rolling to ensure corrosion resistance and formability. The actual tensile strength of the product can reach the 600 MPa .Using a temperature and humidity chamber for cyclic wet-dry tests， along with methods such as SEM analysis， metallographic analysis， corrosion weight loss measurement， and electrochemical analysis， the corrosion resistance of coating-free high-strength and high-corrosion-resistant steel LG500EW， galvanized plain carbon steel Q235， and conventional low-alloy steel Q355B was investigated in a simulated industrial marine atmospheric environment. The results show that in such an environment， both LG500EW and galvanized Q235 exhibit better atmospheric corrosion resistance than conventional low-alloy Q355B. As the simulated accelerated test duration increases， the corrosion rate of galvanized Q235 continues to rise until corrosion occurs beneath the coating on the iron substrate. In contrast， with prolonged exposure， a protective rust layer gradually forms on LG500EW steel. The outermost rust layer develops a relatively dense and complete plate-like corrosion product layer， with a significant increase in the diffraction peak intensity of α-FeOOH in the corrosion products. The self-corrosion potential rises while the self-corrosion current decreases. After 32 days of corrosion， the corrosion thinning of LG500EW steel is 90 μm， approximately twice that of galvanized Q235 （40 μm）， demonstrating excellent corrosion resistance.The environmentally friendly， coating-free， high-strength， and high-corrosion-resistant highway guardrail steel exhibits superior performance in industrial marine atmospheric environments compared to traditional guardrail steels. The developed steel has been successfully applied in coating-free highway guardrails， yielding significant economic， social， and ecological benefits.