The formation mechanism of small holes on the surface of NAF cross roller bearing rings is that after the passivation film on the metal surface of the bearing is damaged, its surface is in an active dissolution state. Cl-) will undergo electromigration under the action of active metal surface cations, enriched on the surface of the metal anode, causing the corrosion potential of the metal electrode to rise; when the corrosion potential of the metal anode is high to a certain extent, reaching the critical value of forming a corrosion nucleus, The anode is initially dissolved, and the anode current increases sharply, forming pits on the metal surface together.
This is an irreversible reaction, and because the depression on the surface prevents the outward dispersion of anions (Cl-) and metal cations, the hydrolysis reaction of Fe2+ (reversible reaction) is carried out in the depression following the anode dissolution reaction of Fe, The concentration of H+ in the pores increases, and the electromobility process of ions also increases the concentration of anions in the pores. If the anion is Cl-, this is equivalent to continuously increasing the HCl solution into the hole with the development of the corrosion hole.
The above process continues to circulate, and the corrosion pit continues to deepen, forming small hole corrosion. The reason for the damage of the passivation film is that there is inhomogeneity in the chemical or physical properties of the metal surface of the cross roller bearing, such as large compositional fluctuations, non-metallic inclusions, foreign matter adhesion, mechanical damage, oxide film cracks, etc., making The surface passivation film may be damaged.
