Abstract
利用慢應變速率拉伸(SSRT)技術，在開路電位條件下，以各種不同拉伸應 變速率研究黃銅在0.1M鹵化鈉鹽水溶液中(pH=6.8)的應力腐蝕破裂之影響 效應。結果顯示在F-中會產生嚴重的沿晶應力腐蝕破裂(IGSCC)，而且嚴 重性隨應變速率的減少而增加。相對地，在0.1MCl-，Br-或I-溶液中，無 論以何種拉伸應變速率試驗，均不產生應力腐蝕破裂。孔蝕電位Ep和保護 電位Epp與F-濃度的對數關係，以下列方程式存在：Ep=a+blog[F-]及Epp= a+blog[F-]。慢應變速率拉伸(SSRT)的技術，在開路電位及外加電位的條 件下用來研究黃銅在不同氯化鈉(NaF)濃度的溶液中(pH= 6.8)的應力腐蝕 破裂特性。結果顯示造成黃銅IGSCC最小氟化鈉濃度為1x10-4M，而此一濃 度也是造成再鈍態保護所需的最小濃度。在較鈍性電位和低於Cu2O範圍的 陰極電位，都屬於延性破壞。在充飽和空氣溶液中，產生IGSCC的最小氟 鹽濃度為 1x10-4M，但是在充飽和氮氣和氧氣溶液中，此一臨界濃度上升 至1x10-2M苯並三挫在氟鹽溶液中，隨著溶解氧氣的增加對黃銅的IGSCC及 電化學溶解腐蝕有更佳的抑制效果。研究電漿氮化的304，410不□鋼 及4140低合金鋼在3% NaCl溶液中的腐蝕及磨耗腐蝕的行為。結果顯示， 電漿氮化的SAE 4140鋼因會有一厚而緻密的保護層，可阻止抑制鐵的陽極 溶解腐蝕，然而電漿氮化的304及410不□鋼因含有氮化鉻(CrN)的析出， 藉加速鐵的陽極溶解會造成嚴重的孔蝕。 The slow strain rate tension (SSRT) technique was used to study the effect of strain rate on the susceptibility to stress corrosion cracking (SCC) and crack velocity of 67/33 brass in 0.1M sodium halide solutions (pH=6.8) at 25C. The results indicate that F- ions induce a significant suscept- ibility to intergranular stress corrosion cracking (IGSCC) and that susceptibility increases with decreasing strain rate. In contrast, in 0.1M Cl-, Br-, or I- solutions, no SCC susceptibility was observed, regardless of the strain rates used. Pitting potentials, Ep, and protection poten- tials,Epp, have been determined for brass (33% Zn) using a cyclic polarization method.The pitting potentials, Ep, and protection potentials, Epp, depend on the logarithmic concentration of F- ions according to the equations: Ep=a+blog[F-] and Epp= a+ blog[F-]. The minimum concentration of NaF solu- tions that caused intergranular stress corrosion cracking (IGSCC) was 1x10-4M. This concentration, was also the critical level for repassivation, ob- served in cyclic polarization tests. In the presence of 10-1M NaF the potential range for IGSCC was -150 to -50mV(SCE). In aerated solutions, a minimum fluoride con- centration of for producing IGSCC was found to be 1x10-4M, whereas the threshold concentration shif- ted to 1x10-2M in both nitrogen- and oxygen-satur- ated solutions. There exist a critical fluoride concentration of 10-1M as solution exposed to air or saturated with air, showing the most serious IGSCC susceptibility and corrosion rate of 67/33 brass. BTA was a favorable inhibitor of IGSCC and electrochemical dissolution of 67/33 brass as dis- solved oxygen increases.