Corrosion Behavior of 5052 in 6061 Aluminum Alloys in Deep Sea Environment

Corrosion Behavior of 5052 in 6061 Aluminum Alloys in Deep Sea Environment

Aluminum alloy has low density, high fatigue resistance, high specific strength and specific stiffness. Je eden izmed konstrukcijskih materialov iz neželeznih kovin, ki se pogosto uporablja v industriji. Ima dobro odpornost proti koroziji in se vedno bolj uporablja v pomorskem inženirstvu. Obsežen. The accumulation of foreign aluminum alloy real sea exposure corrosion data began with the exposure experiments in the Panama Canal area in the 1940s.

5052 aluminijeve zlitine

Od 1962 do 1970, the U.S. Navy carried out large-scale real sea exposure experiments in Port Wynemee, California.

The exposed materials include as many as 475 kinds of alloys, vključno z 7 kinds of aluminum alloys such as 1100, 2014, 3003, 5052, 5083, 6061 in 7002. Not only the corrosion exposure experiments in shallow seas have been carried out, but also the deep sea conditions in the range of 700-2000m have been carried out. Study on the corrosion performance of the following materials.

Kemična sestava 5052 in 6061 aluminijeve zlitine

Effect of Alloying Elements on Corrosion Resistance of Aluminum Alloy

Alloying elements in aluminum alloys mainly affect their candle resistance by forming different inclusions and alloys [M, 11, 14-22].

The main formation of 5052 aluminijeve zlitine is Al6 (Fe, Mn) intermetallic compound and P phase (Mg2Al3). The potential of Al6 (Fe, Mn) intermetallic compound is about -700mV (psSCE, the same below), which is slightly higher than that of the matrix The potential (-800mV) exists as the cathode phase; while the Lu phase (Mg2Al3) potential is about -920mV, which is slightly lower than the potential of the matrix, acting as the anode 116_181.

Corrosion rate of 5052 in 6061 aluminum alloys in deep sea

Za 6061 aluminijeve zlitine, glavna tvorba je nečistoča faza A1Fe-Si in faza Mg2Si. Potencial faze A1Fe-Si je približno -200mV, ki je veliko višji od potenciala matrice, in obstaja kot katodna faza; potencial faze Mg2Si je okoli -1200mV, daleč pod potencialom substrata, deluje kot anoda 119_221.

Obe drugi fazi in matrika iz aluminijeve zlitine tvorita mikropar. The 5052 in 6061 aluminijeve zlitine imajo zaradi različnih mikrostruktur različne učinke mikroparov. Nizko potencialna faza Mg2Al3 v 5052 aluminijeva zlitina je prednostno korodirana kot anoda, in A1- Fe-Mn faza ima velik potencial glede na substrat, kar bo pospešilo korozijo okoliške podlage. Od druge faze Mg2Si, ki ima nizek potencial v 6061 aluminijeve zlitine, has a very low potential relative to the substrate, it acts as an anode and corrodes preferentially; the Al-Fe^Si phase Relative to the substrate potential is very high, as the cathode phase, it will promote the corrosion of the surrounding substrate, and accelerate the corrosion of 6061 aluminijeve zlitine.

5mm debeline 6061 aluminijeve zlitine

V primerjavi z 5052 in 6061 aluminijeve zlitine, the two phases in 6061 aluminijeve zlitine have a larger potential difference, and the effect of microcouples is greater, which is prone to pitting corrosion. After pitting corrosion occurs, it will grow rapidly and eventually cause corrosion perforation. .The potential difference between the two phases in the 5052 aluminum alloy is smaller than that of the 6061 aluminijeve zlitine, and the microcouple effect is small, and its pitting degree is slightly lower than that of the 6061 aluminijeve zlitine. Changes in corrosion performance.

Influence of Deep Sea Environmental Factors on Corrosion of Aluminum Alloys

The ignition of aluminum alloys can be divided into two stages, to je, the pitting nucleation stage and the pitting growth stage. There are three main theories about the reasons for the rupture of the passivation film and the metastable pitting nucleation, namely, the ion penetration mechanism, Passivation film rupture mechanism and adsorption mechanism Among them, the chloride ion penetration mechanism is considered: when aggressive anions (such as C1″) are adsorbed on the passivation film, the chloride ion radius is small and easy to pass through the passivation film. Strong induction ions Conductive, so a high current density can be maintained at a certain point on the film, and the cations are promoted to move randomly. When the electric field at the interface of the film solution reaches a certain critical value, pitting corrosion occurs [241. Razvit je bil mehanizem pretrganja pasivacijskega filma Macxloiialdov model točkastega defekta: Agresivni anioni (kot je Cl_) se adsorbirajo na površini oksida in reagirajo s kationi na meji ion/raztopina, kar povzroči nastanek kationskih prostih mest v pasivacijskem filmu. Ta prazna kationska mesta se premaknejo proti transportnemu vmesniku kovina/film, ko prostih mest kationov, ki dosežejo vmesnik kovina/film, ni mogoče porabiti, odvečna prosta kationska mesta se zberejo v "grozde prostih mest", ki učinkovito ločijo pasivacijsko folijo od kovinske podlage, nastajanje jamičaste korozije in adsorpcijska teorija se imenuje jamičasta korozija. Pojav je posledica konkurenčne adsorpcije Cl_ in O126]. Ko se oblikuje korozijska jama, luknjičasta korozija se hitro razvije. To je posledica procesa zakisljevanja in avtokatalize znotraj jame: Država (potencial je bolj negativen) postane anoda. Površina aluminijeve zlitine zunaj luknje je še vedno v pasiviziranem stanju, in potencial je bolj pozitiven, da postane katoda; torej, znotraj in zunaj korozijske luknje se oblikuje aktivacijsko-pasivacijska mikrotočkovna parna korozijska celica; kovina v korozijski luknji Anodna reakcija v porah se lahko izrazi kot kopičenje produktov korozije (A1203, SiO2, in majhno količino Mg3(S04)2(0H)2 in NaCl) na ustju korozijske jame, postopoma nastane zamašena celica, ki ovira nastajanje por. Migracija notranjih in zunanjih ionov ter difuzija raztopljenega kisika. Baterija koncentracije kisika se oblikuje znotraj in zunaj luknje; the high acidity and high chloride ion concentration environment in the hole promotes the further corrosion of the metal in the hole, thus forming an autocatalytic process of the blocked battery.

Analysis conclusion

• (1) The corrosion rate and maximum pitting depth of 5052 in 6061 aluminum alloys in the environment of 1200m in the South China Sea are lower than those in the environment of 800m in the South China Sea. In the same environment, the corrosion rate and maximum pitting depth of 5052 aluminum alloy The pit depth is much lower than that of 6061 aluminijeve zlitine.
• (2) The comparative analysis of the experimental data and the relevant literature data shows that with the increase of water depth, the maximum pitting depths of 5052 in 6061 aluminum alloys first increase and then decrease, and the maximum pitting depths appear at a water depth of about 800m.
• (3) Oba 5052 in 6061 aluminijeve zlitine so imele razpokano korozijo in perforacijo v območju kovičenja, in režna korozija 5052 aluminijeve zlitine je bilo resnejše, v odseku je prišlo do resne žlebove korozije: 5052 in 6061 aluminijeve zlitine so bile v glavnem Na površini se je pojavila luknjičasta korozija, in jamica za svečo na površini 6061 aluminijeva zlitina je bila globlja in gostejša, luknjice in perforacije so se pojavile v 800 m globokem morskem okolju.
• (4) Produkti bele korozije na površini 5052 in 6061 aluminijeve zlitine so sestavljene iz A1203, Si02, in majhno količino Mg3(S04)2(0H)2 in NaCl.