Corrosion Effect in Carbon Steel: Process Modeling Using Fuzzy Logic Tools

Round 1

Reviewer 1 Report

Manuscript title: Corrosion effect in carbon steel: Processes modeling with fuzzy  logic tools

The manuscript describes the application of fuzzy logic tools and Mathlab for the study of corrosion of carbon steel  in acidic media.  The manuscript needs a minor revision before it can be considered for publication.

1)      Minor language correction are required for the smooth flow of the manuscript

2)      Write briefly on the control parameters employed in the application of fuzzy tools and Mathlab

3)      What is the advantage of this fuzzy tool over other established tools for the theoretical studies.

4)      Whether the theoretical studies have been compared with experimental data in literature?  

Minor language corrections are required for the smooth flow of manuscript

Author Response

Reviewer 1

The manuscript describes the application of fuzzy logic tools and Mathlab for the study of corrosion of carbon steel  in acidic media.  The manuscript needs a minor revision before it can be considered for publication.

• Minor language correction are required for the smooth flow of the manuscript

Answer: Done

• Write briefly on the control parameters employed in the application of fuzzy tools and Mathlab

Answer: In the data analysis with fuzzy logic, the fuzzy stage gives the input data a degree of membership within the different possible expressions, for this it searches for the correspondence between the variables state, and the defined membership functions, for such purpose. Therefore, for a certain value of a variable, its degree of membership will be greater in one expression than in the others. Once the variables states are expressed in linguistic form, logical relationships can be established between them, typically through rules such as if...then (IF-THEN). To do this, a series of relationships are defined that interpret the common sense, and allow the generation of a desired action (in a linguistic state). Subsequently, this must be translated into a number (defuzzification), so that the digital-analog converter converts it to a signal. We think this explanation is too dense to put in the paper, but if reviewer finds this explanation important, we can add it in the paper in fuzzy methodology section.

• What is the advantage of this fuzzy tool over other established tools for the theoretical studies.

Answer: The main advantage of applying fuzzy logic instead of classical statistics lies in the ability to discriminate between variables for models formulation, in fact, while statistics are used to discriminate or classify a binary language such as "yes or no", "white or black” the fuzzy admits infinite intermediate values ​​such as an infinite range of grays between white and black, which makes it possible to observe phenomena or interrelationships that are not detectable with statistics. It is also more intuitive and easy to use. This is now explained from lines 143 to 146.

• Whether the theoretical studies have been compared with experimental data in literature?  

Answer: Yes, different authors have previously used this technique using data matrices that wee used to formulate operating models of water-mining-environment systems with classical statistics which were later validated with fuzzy logic. See references nº 8, 38, 39, 46.

Reviewer 2 Report

1. At line 281, authors state that "The fact that a weight loss and a decrease in the volume of the plates were observed as time goes by, is something to be expected due to the mechanical abrasion processes that eliminate the oxide and sulfate layers formed during the process to continue with the Fe oxidation of the steel." Please give some evidance about this ststement.

2.At line 299, authors state that "The similar behavior between the TDS and the conductivity corroborates the one observed by classical statistics [45] and may be due to an increase in the Fe2+ ion in the water as the oxidation process of the plates progresses." Please give some evidance about this statements.

3.At line 199, authors state that "The consequent variables selected for the study were weight loss and exposure time." Can authors explain why choose those two variables?

4.At line 312, authors states that "It was observed how this corrosion process of the steel plates caused changes in the physico chemistry of the water and has led to a notable increase in TDS and conductivity, as well as a decrease in pH due to oxidation-reduction and precipitation-dissolution processes that occurs in the system." Please give some discussion about the "precipitation-dissolution processes" statement.

Author Response

Reviewer 2

1.At line 281, authors state that "The fact that a weight loss and a decrease in the volume of the plates were observed as time goes by, is something to be expected due to the mechanical abrasion processes that eliminate the oxide and sulfate layers formed during the process to continue with the Fe oxidation of the steel." Please give some evidance about this ststement.

Answer: Corrosion in steel has different natures depending on the environment, material and exposure. In this case, generalized corrosion develops over the entire surface, consisting in the steel progressive oxidation and, consequently, the the section reduction. This type of corrosion, typical in metallic materials exposed to very aggressive environments, is identified with a continuous penetration of oxidation into the material and its subsequent weakening, causing the reduction of the section. Please see new section on lines 287-292.

2.At line 299, authors state that "The similar behavior between the TDS and the conductivity corroborates the one observed by classical statistics [45] and may be due to an increase in the Fe2+ ion in the water as the oxidation process of the plates progresses." Please give some evidance about this statements.

Answer: The Fe in the plates is like Fe(0) and when it oxidizes in this acid medium, it initially becomes Fe(2+) which is soluble in water for that pH value. Subsequently, by hydrolysis, Fe (2+) passes to Fe (3+) that precipitates as ferric oxide or ferric hydroxide or ferric hydroxysulfate that are less soluble than the previous one. Please see new section on lines 300-303.

3.At line 199, authors state that "The consequent variables selected for the study were weight loss and exposure time." Can authors explain why choose those two variables?

Answer:The choice of these consequents is linked to the formulation of the proposed model; both the plates weight loss and the exposure time to the acid medium are clear indicators of how the metallic elements are affected. As longer the plate is submerged in the acid, as greater the weight loss and with it the rest of the variables will vary. It is read as follows: When weight loss takes, for example, a "extremely low" value, then the other variables take the following values.....It is also formulated like this: when the exposure time is “extremely high,” then the other variables present values........ See new sentence on Lines 202-203.

4.At line 312, authors states that "It was observed how this corrosion process of the steel plates caused changes in the physico chemistry of the water and has led to a notable increase in TDS and conductivity, as well as a decrease in pH due to oxidation-reduction and precipitation-dissolution processes that occurs in the system." Please give some discussion about the "precipitation-dissolution processes" statement.

Answer: The transition from ferrous to ferric and the oxidation of iron in general is done at the expense of oxygen in the water, therefore, if we remove oxygen from the water, what is released are hydrogen ions (H+), remember that the water acidity is inverse of pH which is a function of the hydrogen ion concentration. Hydrolysis is a chemical reaction in which the addition of water causes the breaking of molecular bonds. Chemically, iron is an active metal that combines with many other elements and easily oxidizes in the presence of water. Displaces hydrogen from mosto f the acids.The precipitation of oxides and sulfates in an acid medium is the response of the medium itself to the arrival of the fluid at its saturation limit.

Reviewer 3 Report

Text prepared correctly. However, it cannot be accepted in this form. Illegible drawings - no explanations to the drawings. Figure 1 - how the min and max. values ​​are determined ?

If the carbon content in the tested steel is below 0.25%, it is low carbon steel (not carbon steel).

Correction should be submitted

 

Author Response

-Text prepared correctly. However, it cannot be accepted in this form. Illegible drawings - no explanations to the drawings. Figure 1 - how the min and max. values ​​are determined ?

Answer: The images were modified and showed in high quality so that they are easily observable. On the other hand, Figure 1 is simply an example, it does not represent any specific variable. However, and as detailed in the paper, the maximum and minimum are the maximum and minimum values ​​obtained from the variable under study. Therefore, it is considered that the discourse universe is all the values ​​that the variable can take between the maximum and the minimum obtained from all the analyzed data.

-If the carbon content in the tested steel is below 0.25%, it is low carbon steel (not carbon steel).

Answer: The so-called carbon steels have different carbon %, obviously depending on the desired mechanical characteristics. The addition of a higher carbon % unequivocally determines a greater resistance of the steel and a lower ductility. Therefore, the use of these steels with low carbon content in the construction sector is normal, especially for beams and columns. Therefore, the denomination of carbon steels corresponds to those steels, which obviously have carbon, and in turn have a reduced alloy content. That is to say, to consider a carbon steel the true limitation is the content and type of alloys that it presents, not so much the carbon %.

Round 2

Reviewer 3 Report

article prepared correctly. Answers given correctly