Measures to avoid and eliminate hydrogen embrittlement

( 1) , reduce the number of hydrogen permeability in must try to reduce the high strength/high hardness steel fasteners, pickling, because acid can increase hydrogen embrittlement. When rust removal and oxide skin, try to adopt the method of sand blasting, if rockwell hardness is equal to or greater than the HRC 32 fasteners for pickling, must ensure parts when making pickling process in the acid soaking time the longest do not exceed 10 minutes. And should try to reduce the concentration of acid, and ensure the parts in the acid soaking time not more than 10 minutes; When oil removal, use cleaner or chemical oil removal methods, such as solvent degreasing seepage hydrogen quantity is less, if using electrochemical oil removal, anode and cathode before high strength parts are not allowed to use the cathode electric lift oil; During heat treatment, strictly control the drip of methanol and propane; When plating, alkaline solution or high current efficiency of plating solution is less hydrogen permeability. ( 2) , using low diffusible hydrogen and hydrogen solubility of plating coating is generally believed that in Cr, zinc plating, Cd, Ni, Sn, Pb, seeping into the steel easy remnant of hydrogen, and Cu, Mo, Al, Ag, Au, W and other metal coating with low diffusible hydrogen and the hydrogen solubility, less hydrogen permeability. Could satisfy the requirement of product technical conditions in the circumstances, can be used not cause hydrogen permeability of coating, such as mechanical galvanizing or chromium-free zinc aluminum coating, not happen hydrogen embrittlement, high corrosion resistance, good adhesion, than electroplating and environmental protection. ( 3) , stress before and after the plating to hydrogen to eliminate hydrogen embrittlement hidden trouble if parts after hardening, welding process, such as the internal residual stress is larger, should carry on the tempering treatment before plating, tempering eliminating stress can actually reduce the amount of parts within the trap, so as to reduce the occurrence of hydrogen embrittlement. (4), control of thickness of coating the surface coating covered in fasteners, coating to a certain extent can have the effect of hydrogen diffusion barrier, it will hinder the diffusion of hydrogen to fasteners. When the coating thickness more than 2. 5 microns, hydrogen diffusion in tight firmware out is very difficult. Therefore hardness < 32 HRC fasteners, coating thickness can ask in 12 microns; Hardness of 32 HRC or high strength bolt, coating thickness should be controlled in eight mu mmax. This request in product design, it must be considering the risk of hydrogen embrittlement of high strength bolt, rational selection type and coating thickness of coating. In general, in addition to local hardening type fasteners, hardness more than 49 HRC of high strength steel parts are not allowed to take the form of surface treatment of electroplating.