To reduce the amount of hydrogen penetration in 12Cr1MoVG alloy pipes, it is essential to minimize the acid pickling of high-strength/high-hardness T22 alloy steel pipes, as acid pickling can exacerbate hydrogen embrittlement. When removing rust and oxidation scale, it is preferable to use sandblasting and shot peening methods. For 12Cr1MoVG alloy pipes with Rockwell hardness equal to or greater than HRC 32 that require acid pickling, ensure that the immersion time of the T22 alloy steel pipes in the acid does not exceed 10 minutes during the acid pickling process. Additionally, strive to lower the concentration of the acid solution and ensure that the parts are immersed for no more than 10 minutes. For degreasing, use cleaning agents or solvents for chemical degreasing, as this method has less hydrogen penetration. If electrochemical degreasing is used, start with the cathode and then the anode; high-strength 12Cr1MoVG alloy pipes are not allowed to be degreased using cathodic electrolysis. During heat treatment, strictly control the dosage of methanol and propane. During electroplating, alkaline plating solutions or plating solutions with high current efficiency have less hydrogen penetration.
【2】Low hydrogen diffusivity and low hydrogen solubility coatings adopted
It is generally believed that hydrogen渗入 during electroplating of materials like Cr, Zn, Cd, Ni, Sn, and Pb tends to remain in steel components. However, alloys such as Cu, Mo, Al, Ag, Au, and W, including the 12Cr1MoVG alloy tube coatings, exhibit low hydrogen diffusion and solubility, resulting in less hydrogen penetration. Under the condition of meeting product technical requirements, coatings that do not cause hydrogen penetration can be used, such as mechanical zinc plating or chrome-free zinc-aluminum coatings. These coatings prevent hydrogen embrittlement, offer high corrosion resistance, good adhesion, and are more environmentally friendly than electroplating.
Pre-plating stress relief and post-plating dehydrogenation to eliminate hydrogen embrittlement risks: If parts have significant internal residual stress after processes like quenching and welding, pre-plating tempering should be conducted. The tempering process to relieve stress can actually reduce the number of traps within the parts, thereby mitigating the risk of hydrogen embrittlement.
【4】Controlling the coating thickness, as the coating covers the surface of fasteners, it serves as a hydrogen diffusion barrier to some extent, hindering hydrogen from diffusing outward from the fastener. When the coating thickness exceeds 2.5μm, it becomes extremely difficult for hydrogen to diffuse out of the fastener. Therefore, for fasteners with a hardness of <32HRC, the coating thickness can be required to be 12μm; for high-strength bolts with a hardness of ≥32HRC, the coating thickness should be controlled at a maximum of 8μm.
