The main factor affecting bond strength - oxidation

       oxidation

 

     As mentioned earlier, oxides on the surface of the substrate, solidified particles, and droplets can alter wettability and increase the likelihood of porosity. Not only that, the loose texture of some metal oxides will directly compromise the strength of the coating. Even if the inter-particle voids are filled, the presence of metal oxides greatly compromises the coating's own strength and bonding strength. When cracks are formed in the coating under the action of thermal stress, most of the cracks occur between particles. This is not unrelated to the presence of oxides.

 

     The size of the droplets varies in their sensitivity to oxidation. Small droplets oxidize more easily than larger droplets. On the one hand, the small droplet has a large specific surface area, strong surface activity, and is easy to oxidize; on the other hand, the small droplet has a small mass, and it is easier to fly to the periphery of the flame under the action of the airflow, and lose the original protection condition. Under contact with the outside air to oxidize, resulting in poor bonding performance.