Preparation And Corrosion Resistance Of Layered Double Hydroxide Film On Q235 Steel

Iron and steel are easy to be corroded in atmosphere,soil,ocean and other environments.At present,researchers from all over the world have developed a variety of protective measures,such as surface modification and electrochemical protection.Layered double hydroxides（LDHs）is a kind of metal compound hydroxide with layered structure and the interlayer anion exchangeability of LDHs can be used in metal corrosion protection.Our research synthesized LDHs film on the Q235 substrate and significantly enhanced the corrosion resistance of the substrate.In this paper,Zn Al-Mo O₄-LDHs film was synthesized on the surface of Q235steel with aluminizing process,hydrothermal process and ion-exchange method.The film was uniform and compact with the plate-like structure and the grain grew vertically on the substrate.The current density of the sample decreased to0.388μA·cm^-2 and the polarization resistance increased to 7.66×10⁴Ω?cm².Secondly,Ce O₂ powder were added into the aluminizing process to enhance the corrosion resistance and the mechanical property of the aluminized layer.Then the Zn Al-Mo O₄ LDHs film was synthesized on this substrate.However,the corrosion resistance of this film was almost the same as the Zn Al-Mo O₄LDHs film which was synthesized on the aluminized Q235 sample without the addition of Ce O₂.To further improve the anti-corrosion capability of the LDHs film,the rare earth elements Ce was added into the hydrothermal process as one of the components of the LDHs layer.The Zn Al Ce-Mo O₄ LDHs film and Zn Al Ce-LA LDHs film were synthesized successfully on the aluminized Q235 steel.The current density of these two films decreased to 0.230μA·cm^-2 and 0.107μA·cm^-2,and the polarization resistance increased to 8.69×10⁴Ω?cm² and 1.63×10⁵Ω?cm².Moreover,Zn Al Ce-LA LDHs film has great hydrophobic property with the water contact angle reaching to144.1°.The corrosion protection mechanism of the LDHs film can be included into three aspects.Firstly,the LDHs film can separate the substrate from the corrosive medium.Then Zn²⁺and Ce³⁺can be released from the LDHs layer and combined with OH^-in the solution to form hydroxides on the substrate.Moreover,the interlayer anion in LDHs can catch the corrosive Cl^-and the Mo O₄^2-and LA released from LDHs film can form an inhibiton layer on the substrate.All of the above factors provide the Q235substrate great corrosion resistance.