Correlating corrosion inhibition to grain size in electrodeposited Ni-18Co
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ORIGINAL ARTICLE
Correlating corrosion inhibition to grain size in electrodeposited Ni-18Co Srikant Gollapudi 1
&
Wenjun Cai 2 & Supriya Patibanda 3 & Koteswararao V. Rajulapati 3 & Lakshman Neelakantan 4
Received: 22 September 2020 / Accepted: 23 October 2020 # Qatar University and Springer Nature Switzerland AG 2020
Abstract This work describes corrosion studies on electrodeposited Ni-18Co bearing grain size in the nanocrystalline, ultra-fine-grained and microcrystalline range. The as-received Ni-18Co sheet had a nanocrystalline structure with an average grain size of 30 nm. Controlled annealing experiments at 500 °C and 700 °C provided material with average grain size values of 660 nm and 4.8 μm, respectively. Corrosion studies were conducted on the as-received and annealed material in de-aerated 0.1 M H2SO4. An inhibitor tryptamine was also added to the electrolyte for selected experiments to understand grain size-corrosion resistance correlations in the presence of the inhibitor. The inhibitor was found to mildly enhance the corrosion resistance of the nanocrystalline material but had negligible effect on the corrosion behaviour of the 500 °C and 700 °C annealed samples. The icorr of the nanocrystalline material was 9 × 10−6 A/cm2 which reduced to 5.3 × 10−6 A/cm2 on the addition of the inhibitor. On the other hand, the icorr of the 500 °C and 700 °C annealed samples were 10 × 10−6 A/cm2 and 10.3 × 10−6 A/cm2, respectively, which reduced marginally to 9.1 × 10−6 and 10.2 × 10−6 A/cm2 on the addition of the inhibitor. Microhardness measurements of the three materials revealed a reduction in the hardness following annealing with the hardness of the nanocrystalline material at 4100 MPa which reduced to 2250 and 1050 MPa for 500 °C and 700 °C annealed samples. Keywords Nanocrystalline . Corrosion . Grain size . Inhibition
1 Introduction Ralston and Birbilis [1] conducted a thorough review to understand the effect of grain size on the corrosion behaviour of metallic materials. Ralston and Birbilis [1] and Ralston et al. [2] outlined the different conditions under which grain size could have (a) positive, (b) negative and (c) neutral influence on corrosion resistance. For example, grain refinement in pure Mg was found to improve corrosion resistance when the material was tested in neutral or alkaline NaCl solutions [3–6].
* Srikant Gollapudi [email protected] 1
School of Minerals, Metallurgical and Materials Engineering, IIT Bhubaneswar, Bhubaneswar, India
2
Department of Materials Science and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
3
School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad, India
4
Metallurgical and Materials Engineering, IIT Madras, Chennai, India
Similarly, recent work by Wasekar et al. [7] on nanocrystalline Ni-W alloys revealed an improvement in corrosion resistance with grain refinement. The improvement in corrosion resistance in both pure Mg and nc Ni-W is attributed to the superior nature of the passive
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