**7. Results and discussion**

#### **7.1 Quality of electrodeposited zinc**

The quality of the electrodeposited zinc was observed through the deposit parameters as the brightness, the strength adhesion and the thickness. The obtained *Reducing Emerging Contaminants Ensuing from Rusting of Marine Steel Installations DOI: http://dx.doi.org/10.5772/intechopen.95493*

results are presented in **Table 1** for MDE, **Table 2** for EAE and **Table 3** for BE. Where: + adhesion is strong, ++ adhesion is very strong.

Via **Tables 1**–**3** we noted that there is an increase in the deposited mass, thickness and adhesion when increasing the concentration of MDE (1.6 g/l). However, for EAE and BE, these parameters reached a maximum value at 1.2 g/l and then decreased, indicating that the better deposit (nucleation and growth) is found in these concentrations. The obtained results may be related to two considerations: the first one is that the adsorption of additives on the surface, leads to a partial coating of the steel, thus blocking the active sites and causing a decrease in the nucleation rate. The second consideration is that the additive will complex with one of the electroactive species in the solution, therefore the step of dissociation of the complex introduces a new kinetic constant before the redox reaction of the electroactive species at the electrode surface [22]. Furthermore, and according to ASTM D 523 [23] regulations, we observed that the deposits obtained with the addition of the extracts were matt. However, when adding different concentrations (1.2; 1.4 and 1.6 g/l) of BE, the deposits were semi-gloss. In addition, all measured thicknesses were in agreement with ASTM A879 and ASTM B633 [24].

#### **7.2 Potentiodynamic polarization measurement**

The corrosion resistance of the electrodeposited mild steel was tested in seawater at 298 K to evaluate the effect of adding extracts to the chloride baths. The electrochemical parameters such as Ecorr, icorr and CR are collected in **Table 4** for MDE, **Table 5** for EAE and **Table 6** for BE.

From **Tables 4**–**6**, it can be seen that the addition of the investigated extracts as additives gave rise to significant decreases in current densities as well as the corrosion rate compared to the sample obtained without extracts addition. This indicates that the studied extracts strongly modified the quality of the deposit producing coatings more resistant to corrosion and therefore lessening the formation of biofilms, which represent one of emerging contaminants. It is also noted that the dependence of the


**Table 1.**

*Emerging Contaminants*

sweep rate of 1 mV/s.

**6.7 Gravimetric measurements**

w: average weight loss.

**7. Results and discussion**

**7.1 Quality of electrodeposited zinc**

t: immersion time.

was used to determine the corrosion rate [21]:

A: total area of one mild steel specimen.

**6.4 Experimental conditions**

the bath, cleaned with distilled water and air dried [14].

**6.6 Potentiodynamic polarization measurements**

**6.5 Quality of the deposited zinc layer**

All experiments were carried out in an aerated medium, pH = 5 and current of 0.04 A. The steel sample represents the anode of the electrochemical cell, while the zinc plate represents the cathode leaving a distance of 1 cm between them. The zinc plating of the steel was carried out for 30 min, with gentle stirring, by partially immersing the steel sample and the zinc electrode in the chloride bath. To determine the weight of deposited zinc on surfaces, all substrates were weighed before and after electroplating. At the end of the process, the samples were removed from

The thickness of the deposited zinc layer was measured with an Elektro-Physik (eXacto) apparatus and the adhesion of the coated zinc to the substrate was examined by the ASTM D3359 method [20]. For the adhesion test, an "X" was etched on the film and an attached adhesive tape was applied to the samples, and then removed strongly. This test is macroscopic and more qualitative. The gloss of the zinc deposits was measured using a Poly Gloss meter with a large beam of white light at a measuring angles of 20°, 60° and 85°. Calibration was performed automatically using a highly polished black standard built into the gloss meter. The final

Potentiodynamic polarization measurements were performed in seawater with the coated samples as working electrode, a platinum rod as counter electrode and a saturated calomel electrode (SCE) as a reference electrode. A controlled computer (Voltalab PGZ 301) instrument with Voltamaster 4 software was employed for this purpose. The measurements were applied in the potential range of ±1500 mV at a

To evaluate the corrosion resistance of the electrodeposited substrates, weight loss measurements were made. Each sample coated in chloride baths containing different concentrations of the extracts was partially immersed in seawater (corrosive medium). Measurements were collected every five days for a month and the Eq. (1)

<sup>=</sup> <sup>w</sup> CR

The quality of the electrodeposited zinc was observed through the deposit parameters as the brightness, the strength adhesion and the thickness. The obtained

At (1)

gloss values were the average of three measurements taken for each coating.

**294**

*Mass, thickness, brightness and strength adhesion of the deposited zinc layer in the presence of MDE.*


**Table 2.**

*Mass, thickness, brightness and strength adhesion of the deposited zinc layer in the presence of EAE.*


**Table 3.**

*Mass, thickness, brightness and strength adhesion of the deposited zinc layer in the presence of BE.*


#### **Table 4.**

*Polarization parameters for corrosion of electroplated mild steel without and with different concentrations of MDE at 293 K.*


#### **Table 5.**

*Polarization parameters for corrosion of electroplated mild steel without and with different concentrations of EAE at 293 K.*

density of the corrosion current and the additive concentration in the electroplating bath was not linear, probably due to the fact that in each electroplating process there is an optimum additive concentration, whereby the deposit quality is the best [25].

#### **7.3 Gravimetric measurements**

**Figure 1** shows the corrosion rate curves of the mild steel in the absence and in the presence of optimal concentrations of *Taxue baccata* extracts used as additives during their immersion in seawater for one month.

**Table 7** gathers the values of the corrosion rate in the absence and in the presence of optimal concentrations of *Taxue baccata* extracts tested separately as additives in zinc baths.

The examination of **Table 7** and **Figure 1** displayed a better corrosion resistance for all plated samples in the presence of optimal concentration of extracts as additives than those plated in their absences. Furthermore, the plated sample without additives recorded a corrosion rate value of 0.0052 (mg cm−2 h−1) during one month of immersion time in seawater. In contrary, the corrosion rate values for plated specimens with additives were in the range of 0.0025 and 0.0018 mg cm−2 h−1.

**297**

**8. Conclusion**

Plated with MDE

**Figure 1.**

Plated with EAE

Plated with BE

**Table 7.**

**Substrate C (g/l) Time** 

Unplated / CR (mg/

*concentrations of MDE, EAE and BE.*

**(Days)**

*and with optimal concentration of MDE, EAE and BE.*

cm2 .h)

The obtained results leads to the following points:

*Reducing Emerging Contaminants Ensuing from Rusting of Marine Steel Installations*

**BE extract C (g/l) -Ecorr (V/SCE) icorr (mAcm−2) CR (mm/y)** Without extract / 923.8 0.6514 9.791 With extract 1 1107.6 0.2283 3.431

*Polarization parameters for corrosion of electroplated mild steel without and with different concentrations of* 

1.2 1076.4 0.1287 1.933 1.4 1143.6 0.2631 3.955 1.6 1124 0.3574 5.371

**5 10 15 20 25 30**

0.015 0.0077 0.0054 0.0057 0.0059 0.0056

The obtained values of corrosion rate for the specimen plated in the presence of 1.6 g/l of MDE and 1.2 g/l of EAE and BE were lower than the others. This ascertainment is in good agreement with that obtained from potential polarization.

*Corrosion parameters obtained from weight loss measurements of the electroplated mild steel using optimal* 

Blank / 0.0072 0.0061 0.0052 0.0054 0.0053 0.0052

*Variation of the corrosion rate versus exposure time for unplated and zinc plated mild steel samples without* 

1.6 0.0039 0.0043 0.003 0.0026 0.0028 0.0025

1.2 0.0035 0.003 0.0026 0.003 0.0027 0.0023

1.2 0.0033 0.0024 0.002 0.0019 0.0021 0.0018

As part of the challenge against emerging contaminants, the use of three extracts obtained from *Taxus baccata* as additives in electrdeposition of zinc was evaluated.

*DOI: http://dx.doi.org/10.5772/intechopen.95493*

**Table 6.**

*BE at 293 K.*

*Reducing Emerging Contaminants Ensuing from Rusting of Marine Steel Installations DOI: http://dx.doi.org/10.5772/intechopen.95493*


#### **Table 6.**

*Emerging Contaminants*

**Table 3.**

**Table 4.**

**Table 5.**

*EAE at 293 K.*

*MDE at 293 K.*

**296**

**7.3 Gravimetric measurements**

additives in zinc baths.

during their immersion in seawater for one month.

density of the corrosion current and the additive concentration in the electroplating bath was not linear, probably due to the fact that in each electroplating process there is an optimum additive concentration, whereby the deposit quality is the best [25].

*Polarization parameters for corrosion of electroplated mild steel without and with different concentrations of* 

**Cencentration (g/l) Mass deposited (g) Thickness (**μ**m) Adhesion Brightness (GU)** Without extracts 0.0423 15 + Matt 05.30 1 0.0467 16.10 ++ Matt 13.40 1.2 0.0685 24.83 ++ Semi bright 32.85 1.4 0.0405 14.36 ++ Semi bright 31.45 1.6 0.0393 13.40 + Semi bright 31.75

**MDE extract C (g/l) -Ecorr (V/SCE) icorr (mAcm−2) CR (mm/y)** Without extract / 923.8 0.6514 9.791 With extract 1 1064.4 0.4653 5.442

*Polarization parameters for corrosion of electroplated mild steel without and with different concentrations of* 

**EAE extract C (g/l) -Ecorr (V/SCE) icorr (mAcm−2) CR (mm/y)** Without extract / 923.8 0.6514 9.791 With extract 1 787.8 0.000967 0.01131

1.2 1176.4 0.3220 4.840 1.4 1095.3 0.1427 2.145 1.6 1136.4 0.1411 1.650

1.2 159.2 0.000184 0.002158 1.4 699.2 0.000347 0.005219 1.6 618 0.005706 0.06674

*Mass, thickness, brightness and strength adhesion of the deposited zinc layer in the presence of BE.*

**Figure 1** shows the corrosion rate curves of the mild steel in the absence and in the presence of optimal concentrations of *Taxue baccata* extracts used as additives

**Table 7** gathers the values of the corrosion rate in the absence and in the presence of optimal concentrations of *Taxue baccata* extracts tested separately as

The examination of **Table 7** and **Figure 1** displayed a better corrosion resistance for all plated samples in the presence of optimal concentration of extracts as additives than those plated in their absences. Furthermore, the plated sample without additives recorded a corrosion rate value of 0.0052 (mg cm−2 h−1) during one month of immersion time in seawater. In contrary, the corrosion rate values for plated specimens with additives were in the range of 0.0025 and 0.0018 mg cm−2 h−1.

*Polarization parameters for corrosion of electroplated mild steel without and with different concentrations of BE at 293 K.*

#### **Figure 1.**

*Variation of the corrosion rate versus exposure time for unplated and zinc plated mild steel samples without and with optimal concentration of MDE, EAE and BE.*


#### **Table 7.**

*Corrosion parameters obtained from weight loss measurements of the electroplated mild steel using optimal concentrations of MDE, EAE and BE.*

The obtained values of corrosion rate for the specimen plated in the presence of 1.6 g/l of MDE and 1.2 g/l of EAE and BE were lower than the others. This ascertainment is in good agreement with that obtained from potential polarization.
