The transportation of direct-reduced iron (HBI) is complicated by its high chemical activity, which provokes oxidation and heating. The purpose of this study is to determine the mechanism of secondary oxidation of hot-briquetted iron and to evaluate the factors defining this process. Key results of the study: 1. The oxidation mechanism of HBI briquettes during transportation and storage is represented by electrochemical iron corrosion; 2. The effect of the pore (interstice) surface in a briquette exposed during fracture is limited to 25% of the total reactivity, and decreases as the coarseness of the fracture products in the briquette decreases. 3.The most important factors, which define the secondary oxidation rate are: briquette moisture content, particle size distribution, water pH, open air contact surface, pellet reduction technology and briquette phase composition. Ways to improve the transportability of briquettes relate to managing these factors by optimising briquette cooling, improving the quality of the base pellets, etc.