(1), to reduce the amount of hydrogen in the metal infiltration
Must minimize the high strength / high hardness steel fasteners pickling, pickling can be exacerbated by hydrogen embrittlement.
 
Maximize the use of sand blasting method, rust and oxidation leather, Rockwell hardness equal to or greater than the HRC 32 fasteners for pickling pickling process must be formulated to ensure that the parts soaked in acid the longest no more than 10 minutes. And should try to reduce the concentration of the acid, and to ensure that the parts soaked in acid of not more than 10 minutes; in the degreasing time, the use of a cleaning agent or solvent degreasing chemical degreasing, the small amount of hydrogen permeation, if the electric chemical degreasing, first cathode, anode, high strength parts by cathode electrolytic degreasing not allowed; strict control during the heat treatment, the amount of methanol and propane infusion; when in the electroplating bath of the alkaline bath or high current efficiency and permeability The hydrogen amount less.

 (2), a plated coating of low hydrogen diffusion resistance and low hydrogen solubility

Generally believed that, in the electroplating of Cr, Zn, Cd, Ni, Sn, and Pb, penetrate the steel parts of the hydrogen tends to remain down, and the metal plating layer of Cu, Mo, Al, Ag, Au, W, etc. having a low hydrogen diffusion resistance and low hydrogen solubility of hydrogen permeation less. Meet the technical conditions of product requirements, and can be used without causing hydrogen permeation coating, mechanical galvanized or chrome-free zinc-aluminum coating, no hydrogen embrittlement, high corrosion resistance, good adhesion, and the ratio Plating environmentally friendly.

(3) plated the go stress and plated the dehydrogenase to eliminate hydrogen embrittlement hidden

Parts after quenching, welding processes internal residual stress before plating should be tempered, tempering eliminate stress can actually reduce the number of parts inside the trap, so as to reduce the hidden dangers of hydrogen embrittlement.

⑷, control of coating thickness

Coating covering the surface of the fastener coating will play the role of hydrogen diffusion barrier to a certain extent, this will hinder the diffusion of hydrogen to external fasteners. When the coating thickness of more than 2.5μm, hydrogen diffused out from the fastener is very difficult. Hardness <32HRC fasteners, plating thickness can be required 12μm; to the hardness ≥ 32HRC high strength bolts, the thickness of the coating should be controlled in 8μmmax. This requires that product design must take into account the risk of hydrogen embrittlement of high strength bolts, a reasonable choice of coating types and coating thickness.

Under normal circumstances, in addition to the local hardened type fasteners, hardness of more than 49HRC high-strength steel parts is not made use of the surface of the processed form of the plating.

 



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