Electrochemical origin for mitigated pitting initiation in AA7075 alloy with TiB2 nanoparticles

A review on pitting corrosion and environmentally assisted cracking on duplex stainless steel

“…The stress concentration model assumes that a large strain field is generated around the square precipitate, which promotes the initiation of pitting corrosion preferentially at this location [Figure 8C1]. A high-stress field has been verified using HAFFT [Figure 8C2 and C3] [96] . Another hypothesis is that pitting corrosion is related to the Cr-depleted zone around the G phase, which is caused by the growth of the G phase.…”

Corrosion performance of nano‐treated aluminum alloy A206 with TiC nanoparticles

“…Since the matrix serves as the dominant cathode with a larger area, this electrochemical potential increase will reduce the galvanic corrosion tendency and mitigate the localized corrosion attack. Thus, nano-treated A206 with TiC nanoparticles could have better corrosion resistance, particularly higher resistance to localized corrosion attacks (as shown in Figures 7,8,10,and 11). Since the nano-treating could additionally tune the (re-)passivation processes (see Figures 9-11), [12,17] these benefits could collaboratively yield a more stable A206 alloy system against corrosion degradation.…”

“…Given all the corrosion results from immersion tests, electrochemical scanning (Figures 4-6), and IGC tests (Figures 10 and 11), the nano-treating effect with TiC nanoparticles against corrosion degradation in A206 could be understood, as shown in Figure 12: A206 is mainly damaged by the rapid localized corrosion, due to the electrochemical difference between GBs and other features like matrix, matrix precipitates, and GB precipitates (GBPs) (Figure 12a). After nano-treated with TiC nanoparticles, with the nanoparticles dominating the GBs and GBPs, [11,12,20] the near-GB electrochemical potential will be generally increased by TiC nanoparticles (about −107 mV vs. SCE) (Figure 12b). Since the matrix serves as the dominant cathode with a larger area, this electrochemical potential increase will reduce the galvanic corrosion tendency and mitigate the localized corrosion attack.…”

“…[10] Nano-treating is different from the traditional concept of nanocomposites, since it does not depend on a high volume percentage of nanophases to enhance mechanical performance. [11][12][13][14][15] In contrast, only a small amount of nanoparticles is added [16,17] to introduce the effective interplays among nanoparticles, α-phase, and innate secondary phases/precipitates at different (post-)processing stages. [14,18,19] The previous study regarding solidification thermodynamics has proven that nano-treating enabled cracking elimination mechanisms for general Al systems [15,20] and showed improved mechanical performance.…”

“…For example, nanoparticle addition (like Al 2 O 3 ) to Al-Cu systems has been found to mitigate pitting corrosion and anodic dissolution speed, [23,24] but the mechanism is not explained. Therefore, even though the benefits of grain refinement, secondary phase modification, and nanophases' inherent stability are known, [11,12] the right choice to combine supreme mechanical properties and antidegradation performance in high-strength Al-Cu alloys is not determined. [25] To the best of our knowledge, no systematic corrosion study focusing on nano-treated A206 alloy or A206 nanocomposites has been reported.…”