Corrosion And Wear Behavior Of 2024 Aluminum Alloy And Its Anodized Film In Seawater

2024 aluminum alloy is widely used in many fields such as aviation,navigation,offshore drilling platform and auxiliary platform due to its excellent properties of lightweight and highstrength.The problem of corrosion caused by harsh marine environment is becoming more and more serious.Corrosion damage will reduce the bearing area of the structure,reduce the structure fatigue performance,and then threaten the navigation safety and decrease the structural life of the body.Though without using the conventional friction parts,but the friction corrosion will also be generated on the components in the marine environment like wave,tide and flow by producing low-frequency reciprocating stress and lash.However,aluminum alloy has a poor wear resistance property as a conventional light alloy.Therefore,in this paper,the corrosion wear behavior and mechanism of aluminum alloy before and after anodic oxidation in marine environment were investigated,and this study will provide the theoretical basis for the choice of seawater corrosion wear and tear environment materials.The corrosion behavior of 2024 aluminum alloy and its anodic oxide film in seawater was studied by using reciprocating pin disc friction tester and electrochemical workstation with Al2O3 ceramics as friction pair.The electrochemical behavior of the material before and after corrosion was studied by means of the dynamic potential scanning method.The microstructure and wear surface morphology of the anodic oxide film were observed by scanning electron microscopy(SEM).The element valence of wear surface was detected by X-ray photoelectron spectroscopy(XPS).In this paper,by applying the cathodic protection potential,the mechanical wear situation was studied under the condition of constant corrosion and friction with shielding corrosive factors,and the interaction between wear and corrosion and the wear amount are calculated according to ASTM G119-09.The corrosion wear behavior and mechanism under load on the aluminum alloy before and after anodic oxidation in the marine environment were studied.The results show:For 2024 aluminum alloy matrix,the main wear mechanism in seawater is abrasive wear and adhesive wear.During the friction process,the corrosion current density increases greatly,the corrosion rate is accelerated,that is to say,wear promotes corrosion.Meanwhile,as the surface oxide film is damaged,the aluminum matrix is exposed to seawater,and complex galvanic battery will be formed between aluminum matrix and the segregation phase of?phrase and S phase along the grain boundary,leading to electrochemical corrosion and intergranular corrosion.Under the action of alternating stress,stress corrosion cracking(SCC)will be produced,and then develops into cracks,resulting in accelerated spalling of the material,that is to say,corrosion accelerates wear.In the seawater environment,the wear effect of the 2024 aluminum alloy is obviously greater than that of the corrosion process.The mechanical factors are the main factors that cause the corrosion wear weight loss.At the same time,the interaction between corrosion and wear can't be neglected.The interaction between corrosion and wear is mainly reflected in the facilitating effect of corrosion on wear.For the anodized aluminum alloy,its corrosion wear resistance performance greatly improved.Under the same process conditions,with the oxidation time,the oxide film thickness increases,the pore size enlarges,but the hardness decreases.In contrast,the anodic oxide film structure obtained after oxidation for 30 min,namely,AO-30 anodic oxide film has good wear resistance,and the corrosion current density is the smallest,that is,the best corrosion resistance.Therefore,the corrosion behavior of AO-30 anodic oxide film under different loadings were studied.For AO-30 anodic aluminum oxide,the presence of corrosion when rubbing in the seawater will accelerate the damage of the oxide film,that is,corrosion promotes wear,while the friction will increase the corrosion current density,that is,wear promotes corrosion.When the load is small,the single mechanical factor has little damage to the oxide film,under seawater environment,due to the presence of corrosion factors,pitting or stress corrosion cracking will appear,providing the source of creak for the oxide film to wear and tear,and accelerating wear.So the effect of corrosion promoting wear accounts for a higher proportion of the total wear,for about half of the total wear amount.But when the load is large,the mechanical factors on the oxide film damage is so serious that it begins to the dominating factor of the total wear.At the same time,the proportion of corrosion and wear interaction decreased with the increase of the total wear amount.