The Investigation on Optimum Corrosion Protection Potential of STS 316L in Seawater

Abstract

Austenitic stainless steels have problem such as pitting, intergranular corrosion and stress corrosion cracking, which causes severe damage of structure in spite of high toughness and mechanical strength. To minimize these disadvantages in offshore structures demand of STS 316L which has small amount of C and has Mo is increasing. In this paper, the electrochemical experiments are executed to evaluate the durability at various protection potentials on stress corrosion cracking and hydrogen embrittlement of STS 316L in natural sea water environment. The polarization trend for STS 316L shows the effects of concentration polarization due to dissolved oxygen reduction reaction and activation polarization due to hydrogen gas generation. The turning point of two reactions in the polarization curve presented -0.92 V (vs. Ag/AgCl). The lowest current densities in the potentostatic test and non-correded surface condition of specimens by SEM analysis presented at potentials of 0 ~ -0.9 V and 0.4 ~ -0.9 V, respectively. Synthetically, the optimum corrosion protection range without stress corrosion cracking and hydrogen embrittlement is concluded with the potential range of -0.56 V ~ -0.92 V.

Investigation on SCC and HE of STS 304 austenitic stainless steel for offshore structures

“…And the trend persisted until 0.15 V. Pitting corrosion in seawater is generated by chloride ions. The occurrence of pitting corrosion increased the current density, and current at regions in which pitting corrosion was occurring increased concentrically [5][6][7]. Eventually, passivity was observed when the applied potential was increased toward noble direction, the steady increases in current density resulting from pitting corrosion were observed.…”

Çeli̇ği̇n Korozyon Potansi̇yeli̇ne Enzi̇mati̇k Akti̇vi̇teni̇n Etki̇si̇

“…Bu hipotezlerden bir tanesi, mikroorganizmaların biyofilmde hidrojen peroksit (H 2 O 2 ) açığa çıkarması esasına dayanır [5][6]. 'in deniz suyuna maruz bırakılan paslanmaz çeliklerin açık devre potansiyeli üzerine etkisinin kantitatif olarak değerlendirilmesine imkan sağlar [7][8][9]. Bu çalışmada, yapay deniz suyunda çeliğin serbest korozyon potansiyeli üzerine, enzimatik tepkimeler sonucunda açığa çıkan hidrojen peroksit ve glukonik asidin etkisi araştırılmıştır…”