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.
Recently, there has been increased interest in using aluminum alloys in ship construction instead of fiber-reinforced plastic (FRP). This is because aluminum alloy ships are faster, have a greater load capacity, and are easier to recycle than FRP ships. In this study, we investigated the mechanical and electrochemical properties of aluminum alloys using the slow strain rate and potentiostatic tests under various potential conditions. The optimum protection potential range with
regards to hydrogen embrittlement and stress corrosion cracking was determined to lie between -1.5 and -0.7 V (SSCE). These results can be used as reference data for ship design.
The Al alloy is environmental friendly, easy to recycle, and provides a high added value to fishing boats. Aluminum alloy do not corrode due to the formation of an anticorrosive passive film, such as Al2O3or Al2O33H2O, which resists corrosion in neutral solution. In seawater, however, Cl-ions destroy this passive film. We investigated on several electrochemical tests undertaken to determine the optimum conditions in seawater for corrosion protection of casted AC7AV aluminum alloy. The components of casted AC7AV aluminum alloy are similar with Al-Mg alloys (5xxx series) which are used for ship. Result of electochemical experiment, the optimum protection potential range with regards to hydrogen embrittlement and stress corrosion cracking was determined to lie between-1.3 and-0.7 V(vs Ag/AgCl).
The electrochemical and mechanical properties of welded high-strength steel
were investigated using the slow strain rate test method with a constant applied cathodic potential. No correlations were found with the maximum tensile strength, yield strength, stress at failure, or hydrogen embrittlement. However, the elongation, time-to-fracture, and strain-to-failure ratio decreased as the potential became more negative. These parameters were greatest when the potential was -770mV, regardless of the post-weld heat treatment conditions. The elongation and time-to-fracture increased with PWHT.
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