Study on the characteristics and law of pitting corrosion of titanium
Release time:
May 12,2025
Pitting corrosion of titanium has the following characteristics and laws:
Pitting corrosion of titanium has the following characteristics and laws:
1. In chloride or bromide solutions, the pitting corrosion susceptibility of titanium increases as the temperature rises. The effect of pH on titanium's resistance to pitting corrosion is relatively small. Experimental data show that titanium is not susceptible to pitting corrosion because it has a very high rupture potential of about 100 V in sulfate or phosphate solutions. In contrast, the rupture potential of titanium in chloride solution is about 8~10V, and may be even lower in bromide or iodide solution, only about 1V, so titanium in halide solution is more likely to occur pitting corrosion.
2. When the iron content in titanium is high, its resistance to pitting corrosion decreases. The titanium-iron (Ti-Fe) phase is usually the nucleation site for pitting corrosion. For example, in the case of ruthenium oxide coated titanium anodes used in the chlor-alkali industry, pitting corrosion of the titanium itself can lead to the destruction of the ruthenium oxide coating if the impurity iron content is high.
3. The state of surface pretreatment has a significant effect on titanium pitting corrosion. After vacuum annealing and anodizing, titanium has the highest pitting corrosion potential and is not easy to corrode; while after wet sandpaper polishing, titanium is most prone to pitting corrosion. In addition, under the condition of the same surface pretreatment, grade 3 industrially pure titanium has the highest pitting corrosion potential and the least pitting corrosion susceptibility. Experimental data show that increasing the oxygen content of titanium can increase its pitting corrosion potential, thus improving the resistance to pitting corrosion.
4. Titanium surfaces with rough surfaces or rubbed with metals such as zinc, iron, aluminum, manganese, copper, etc., can promote the occurrence of pitting corrosion. However, certain anions (e.g., sulfate, nitrate, chromate, phosphate, and carbonate) can improve titanium's resistance to pitting corrosion.
5. Pitting corrosion usually occurs and develops in three stages: nucleation, growth and repassivation. Nucleation occurs when titanium is at a potential higher than the rupture potential of the film. With the passage of time, the growth of corrosion spots (holes) can be observed after nucleation. However, since the total area of the corrosion holes is not fixed, the current magnitude cannot be used as a quantitative measure of corrosion hole growth. Repassivation can inhibit the development of pitting corrosion, and in some cases, pitting corrosion may stay in the second stage without entering the third stage, when the corrosion holes will stop developing.
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