| Processing the ocean development, has become a key increasing point of economy in the new century. However, the seawater corrosion of matel is always a big problem for all the ocean industries. Among all the anti-corrosion methods, adding corrosion inhibitor, as an effective, cheap and convenient way, attaches more and more recognition. Recently, the government makes a great effort to environmental protection, so"green"is taken more consideration to the corrosion inhibitor research. Hydrolytic polyacrylamide (HPAM), which is widely used in oil field, has an obsorption with the metal surface, and is eco-friendly as well. Therefore, it could be used as corrosion inhibitor in seawater.About the inhibition effect of HPAM, this thesis mainly covers the following aspects. Firstly, the corrosion behavior of Q235 steel in seawater containing HPAM is investigated, then the variety trend of inhibition rate and concentration is analyzed. Secondly, the absorption of HPAM on mild steel and its inhibition mechanism is studied by quantum chemistry and other methods. Thirdly, HPAM compounded inorgannic inhibitor is tested in seawater system, in order to accumulate data and explore the mechanism as well as application.The methods and conclusions of this thesis respectively as follows,1. The corrosion behavior of Q235 steel in seawater with different HPAM concentration and immersion time, is studied by weight loss, potentiodynamic ploarisation, EIS and macroscopical/ microcosmic investigation. It is found that Q235 steel gets a serious corrosion in natural seawater. After adding a certain concentration of HPAM, the corrode electric current density as well as the corrosion rate decreases. The result is that its inhibition efficiency increases with the increase of concentration, to attain almost 65% since 400mg/L. HPAM is a sort of cathodal corrosion inhibitor, which can be proved by Tafel curves, and its absorption is multilayer.2. The B3LYP (ab innito) method is used to optimize the molecular structure of HPAM. According to the Mulliken charges of every atoms, the N and O in the same side have more negative electric charge, play important roles in reaction with the anodic sites. Through exploring the molecular orbit, is shows that O atom has the most HOMO electron density, therfore it has greater contribution to absorption. Generally, the aborsption effect is the combination of both electrostatic and chemical bond.3. Inhibition effiency of HPAM compounded with ZnSO4 is appraised in normal temperature, with several methods. It shows that ZnSO4 is inefficient when singly used, while compounded with HPAM the inhibition rate increases greatly, obtain 85% at the summit. They produce a better co-ordinary inhibitor. It can be seen from the Tafel curves that they are of mixed-type corrosion inhibitor, which can control both cathodic and anionic reaction. Some complex compound film can be investigated by macroscopical and SEM pictures.Besides, this thesis also includes some research on the relationship between the efficiency of inhibitor and its molecular structure. Conclusions read as follows—the organic with a negative group orπelectron, can make a efficient absorption on metal surface. As a result, the more groups, the higher inhibition rate it has. On the other hand, the positive electrial property is the most important factor for electrostatic absorption, which can be enhanced by some electron acceptor groups. The steady complex compound structure can be propitious to bring on good efficiency. |
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