Dear Dr. Kokilaramani Seenivasan ,

your question is very interesting but also very difficult to address in a synthetic way.

I suggest you the same method that I have recommended, here on RG to a dear friend regarding a similar question, and that is, as the first thing to have a look at some papers, which you have probably already read, which contain the basic characteristics for a corrosion inhibitor:

-Corrosion Inhibitors by C Monticelli

In Encyclopedia of Interfacial Chemistry - Surface Science and Electrochemistry, Pages 164-171 (2018)

Available, as abstract, at: https://www.sciencedirect.com/science/article/pii/B9780124095472134432

-Corrosion Inhibitors – Principles, Mechanisms and Applications – Chapter 13 (2012)

Camila G. Dariva and Alexandre F. Galio

http://dx.doi.org/10.5772/57255

Available at: https://cdn.intechopen.com/pdfs/46243.pdf

-Corrosion Inhibitors – Chapter 10 (2011/2012)

Available at: https://www.uv.mx/personal/rorozco/files/2011/02/CORROSION-INHIBITORS.pdf

When choosing the corrosion inhibitor for your application several things need to be considered before start experimental part:

Materials to be protected

Protection effectiveness timeframe (1 week, 1 month, 1 year, etc.)

Method of application (dip, spray, brush, etc.)

Type of protection required (in process, storage or shipping)

Part handling and fingerprint suppression

Type and thickness of coating residue desired

Storage, packaging and/or shipping conditions (temperature, humidity & seasonal conditions)

Removal methods (if required)

Interaction with subsequent processes, if not removed

Environmental, health and safety requirements

Type of product (Oil/Solvent or Water-based) desired

(Source: Selecting A Corrosion Inhibitor by MILACRON, available at: https://www.milacron.com/selecting-a-corrosion-inhibitor/

In my opinion, however, some interesting indications are still missing from this list, for example:

-Does the corrosion inhibitor act in a closed or open system?

- Need to monitor and / or vary the concentration of the inhibitor itself

- Physico-chemical characteristics of the corrosive fluid with which the material will come into contact (chemical composition, conductivity, pH, etc.) and operating conditions: temperature, flow rate, biological charge, suspended solids. etc.)

- .........

As part of the research we can standardize the greatest number of conditions and evaluate the inhibitory power of a given chemical compound compared to another but in the presence of an industrial application, for it to be successful, we must adapt the inhibition system to the real use which must also be monitored and controlled. I could give you a thousand examples of how it is possible, the variation (sometimes even unwanted) of some process parameters, can cause considerable damage ...

Hoping to have been of help, my best regards, Pierluigi Traverso.

Dear Kokilaramani Seenivasan

One way to predict corrosion products is to use Pourbaix diagram (knowing corrosion potentials and pH). Green inhibitors are mainly adsorption type inhibitors or O2 scavengers, so if inhibit anodic reaction and corrosion potentials increase with inhibitor concentration those are anodic inhibitors. If influences cathodic reaction and corrosion potentials decrease those are cathodic inhibitors. If influence both anodic and cathodic reaction-mixed inhibitors. For the determination of real corrosion product onto the surface, use EDX or XRD.

Thank you, Kokilaramani Seenivasan for this valuable question. In this respect, the trends toward examining the protective effect of green inhibitors on metallic corrosion process and evaluating the protective power of these inhibitors is nowaday by means of two routes. The first is using the weight loss measurement, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. In this regard, the influences of inhibitor package concentration and temperature on the inhibition behaviors are investigated. Secondly, Quantum Chemical Calculations are served to investigate the inhibition process of metallic corrosion at electronic and atomic scales by using Density Functional Theory (DFT) calculations and Monte Carlo simulation methods, respectively. These routes make good approach to examine the relationship between inhibitor structural and electronic properties and the inhibition efficiency. I enclosed two recent research that containing such methodology approach. Hope it is helpful.

Best regards

https://downloads.hindawi.com/journals/ijc/2021/6695299.pdf

https://downloads.hindawi.com/journals/ijc/2021/6662395.pdf

Try NACE International Publication. TM-0172: standard test method – determining corrosive properties of cargoes in petroleum product pipelines. Houston, 6 p. 2001