Effect of Oxidizing Decontamination Process on Corrosion Property of 304L Stainless Steel

Abstract

Corrosion behaviors of 304L stainless steel (SS) and 304L SS with oxides film (preoxidation 304L SS) in 1 g/L potassium permanganate solution of various pH values were investigated by using mass loss, electrochemical measurement and scanning electron microscope (SEM) observation. The results showed that mass loss of 304L SS increases with the increase of sodium hydroxide or nitric acid concentration in 1 g/L potassium permanganate solution. The polarization curves of 304L SS in potassium permanganate solution show that passive zones are destroyed more easily in acid potassium permanganate solution than alkaline potassium permanganate solution. The corrosion ability of acid potassium permanganate (NP) decontamination solution used for 304L SS is more aggressive than alkaline potassium permanganate (AP) solution. The oxide film on the surface of preoxidation 304L SS can be removed completely in two oxidation reduction decontamination cycles, oxidizing solution of which comprised 0.4g/L sodium hydroxide and 1g/L potassium permanganate. The 304L SS and preoxidation 304L SS performed alkaline oxidation reduction decontamination of 3 cycles were reoxidation. The micromorphology of reoxidation specimens was similar to preoxidation 304L SS. Therefore the chemical decontamination of alkaline oxidizing and acid reducing steps had no negative effect on corrosion of 304L SS and reoxidation of 304L SS carried out decontamination.

Optimisation of the chemical oxidation reduction process (CORD) on surrogate stainless steel in regards to its efficiency and secondary wastes

“…Further, the anodic polarisation curves showed passive regions. Similar characteristics of polarisation curves were observed with previous studies (Tian et al, 2019). According to the results of Tafel-extrapolation, passivation effects of KMnO 4 were significantly higher above 6 mM concentration.…”

“…The Chemical Oxidation Reduction Decontamination (CORD) is a world-wide known 2-steps decontamination process (Radó et al, 2007;Wille et al, 1997). In the first step permanganate ion (MnO 4 − ) is used to oxidize the chromium oxide-layer and to release chromate ions (Tian et al, 2019). Permanganate ions are derived from potassium permanganate, which can be used in nitric acid media, which is known as NP CORD or in alkaline media (KOH) which is known as AP CORD.…”

“…In the next step, oxalic acid is added to reduce the permanganate ion to aqueous Mn 2+ ions and to dissolve the Fe and Ni enriched oxide layer from the surface of the alloys (Tian et al, 2019). The whole process is repeated several times.…”

“…In most cases, the remaining oxalic acid is removed from the solutions by addition of H 2 O 2 and the presence of the UV-source (CORD UV technology) (Wille and Bertholdt, 1998). On the basis of technological data the CORD UV process can remove up to 73 kg of corrosion products from a wet surface of 3,300 m 2 , while 2900 L of spent resins wastes were generated (Tian et al, 2019). In another study (55 MW-D 2 O nuclear reactor) the technology resulted in personnel dose rate savings of 4,500 mSv and produced 1370 L of spent resins (Tian et al, 2019).…”

Optimized precipitation process for the treatment of radioactive effluents from Ni-alloy decontamination using a chemical oxidation reduction process

“…In the first step of this process, permanganate ions (MnO 4 − ) are employed to oxidize the chromium oxide layer, resulting in the release of chromate ions. Potassium permanganate can be used as the source of permanganate ions, either in nitric acid media (referred to as nitric permanganate (NP) CORD) or in alkaline media with potassium hydroxide (referred to as alkaline permanganate (AP) CORD) (Radó et al, 2004;Wille et al, 1997;Tian et al, 2019). Another variation of the CORD process, known as HP CORD is typically used and involves the utilization of UV source and permanganic acid prepared from potassium permanganate using a strong acid cation resin (Demmer, 1994;Ocken, 1999).…”