Pitting corrosion of TiN-coated stainless steel in 3 % NaCl solution
Jamičasta korozija nerjavnega jekla s prevleko TiN v 3-odstotni raztopini NaCl

Israfil Kucuk, Cevat Sarioglu
2015 Materiali in Tehnologije  
TiN coatings deposited by arc PVD were characterized by XRD and SEM. In-situ measurements of the corrosion of the substrate and the TiN-coated substrate were made using the corrosion potential (Cor.Pot.), the polarization resistance (PR) method and electrochemical impedance spectroscopy (EIS) in a 3 % NaCl solution as a function of the immersion time. The semiconductor scale formed on the TiN was identified using a Mott-Shottky analysis as an n-type semiconductor with a flat band potential of
more » ... band potential of -0.83 V vs. SCE. The TiN coating (0.5 μm thick) consisted of cubic TiN exhibiting columnar grains, pin holes, voids and porosities. The pitting corrosion of the TiN, observed visually between 1 h and 2 h, was captured by EIS and PR. The electrical circuit (EC) model used for the EIS data supported the degradation of the coating through pitting corrosion, in agreement with the visual observations. The corrosion resistance (polarization resistance) determined by the polarization resistance method (Rp) and the EIS (Rtotal) decreased suddenly during the pitting corrosion. The corrosion resistance of the TiN-coated substrate was greater than the corrosion resistance of the substrate during the approximately 24 h of exposure. Prevleka TiN, nanesena z oblo~nim PVD-postopkom, je bila pregledana z XRD in SEM. In-situ meritve korozije podlage in podlage s prevleko iz TiN so bile izvr{ene z metodo korozijskega potenciala (Cor.Pot.), polarizacijske upornosti (PR) in z elektrokemijsko impedan~no spektroskopijo (EIS) v 3-odstotni raztopini NaCl v odvisnosti od~asa namakanja. Mott-Shottkyjeva analiza je odkrila nastanek n-tipa polprevodne {kaje na TiN s potencialom ravnih nivojev -0.83 V proti SCE. Prevleko TiN (debeline 0,5 μm) sestavljajo kubi~ni TiN s stebrastimi zrni, luknjami, prazninami in poroznostjo. Vidno odkrita jami~asta korozija TiN, opa'ena med 1 h in 2 h, je bila posneta z EIS in PR. Model elektri~nega tokokroga (EC), ki je bil uporabljen za EIS-podatke, podpira degradacijo prevleke z jami~asto korozijo, skladno z vizualnimi opa'anji. Korozijska upornost (polarizacijska upornost), dolo~ena z metodo polarizacijske upornosti (Rp) in EIS (Rtotal) se je nenadno zmanj{ala med jami~asto korozijo. Korozijska upornost podlage z nanosom TiN je bila ve~ja kot korozijska obstojnost podlage med izpostavitvijo okrog 24 h.
doi:10.17222/mit.2013.176 fatcat:tx6mym3dlfazljwktdffwn6ece