**Abstract**

Marine steel installations are usually subject to biocorrosion due to their immersing in seawater. Biocorrosion-causing microorganisms, such as bacteria and fungi, often form biofilms on materials, inducing chemical changes in these materials and in the surrounding liquid medium. The formed biofilms resulting from this phenomenon are considered as emerging contaminants. In this work, in addition to the realization of the electrodeposition of zinc on a steel in chloride bath with various concentrations of *Taxus baccata* extracts as additives using a direct courant supply, the study of the corrosion of the obtained substrates was performed in seawater as an aggressive environment. The efficiency against corrosion was evaluated by potentiodynamic polarizations and weight loss measurements. The coated surface morphology was analyzed using brightness meter, thickness meter and adhesion tests. The experimental results showed that all tested extracts performed the quality of the zinc deposits and their efficiency against corrosion indicating that coated samples in the presence of the extracts were more resistant minimizing the emerging contaminants in seawater.

**Keywords:** *Taxus baccata*, biocorrosion, emerging contaminant, inhibition, electrodeposition

### **1. Introduction**

Emerging contaminants (ECs), also known as emerging organic contaminants [1] and contaminants of emerging concerns (CECs) [2], are a group of natural and synthetic chemicals with their transformation products occurring in water bodies throughout the globe. Actually, these materials, which are also considered as microorganisms (e.i. biofilm) present in the environment, are not monitored and have a high potential of causing environmental damage in addition to be suspected of detrimental effects on ecosystems and human health. It should be noted that as reported in the literature, the exposure to environmental relevant concentrations of ECs caused significant alterations in the microbial community composition and function [3].

The biocorrosion, or microbiologically influenced corrosion (C.I.M), which represent one of the biofilms source is an electrochemical phenomenon of dissolution of a metal affecting all industries, where microorganisms (in particular bacteria) can develop [4]. To minimize the biocorrosion and therefore the emerging contaminants, electrodeposition of zinc is usually used for marine steel installations protection, it is a suitable, fast and cost-effective way to improve the surface hardness, anti-corrosion properties and wear resistance…etc. [5]. The electrodeposition consists principally in the immersion of a steel as an electrode in a container containing an electrolyte and a zinc as a counter electrode. The electrodeposition electrolytes usually contain metal salts, species to increase electrolyte conductivity and additives, added to improve leveling metal and to optimize the properties of the deposited metal (hardness, brightness, corrosion resistance, roughness, porosity, grains size …..) [6]. The clear problem with these additives is that they are all synthetic, toxic, high cost and they have a significant negative impact on the environment, such as furfurale and thiourea [7–11]. To resolve this problem, the new trend in the current research is focused on replacing synthetic additives with less expensive, biodegradable and effective natural products such as extracts obtained from natural products as *Manihot esculenta* [12], *Saccharum officinarum*, *Ananas comosus* [13], *Taxus baccata* [14] and *Daphne gnidium* L. [15].

In this work, two main objectives are targeted. Firstly, we are focused on the use of plant extracts obtained from a plant belonging to Algerian flora (*Taxus baccata*), as additives in chloride baths for the zinc plating of a mild steel (E24–2). Secondly, we will evaluate the effect of the addition of the investigated extracts as additives, namely on the quality of the zinc deposit, on one hand and on the other hand, on the resistance of the deposit against corrosion, therefore the decrease of the emerging contaminants effect.

#### **2. Emerging contaminants**

Emerging contaminants are synthetic or naturally occurring chemicals or any microorganisms that are not commonly monitored in the environment but have the potential to penetrate in the environment and thereby causing known or suspected adverse ecological and/or human health effects. These contaminants consist of pesticides, pharmaceuticals, personal care compounds, industrial additives byproducts, food additives, water treatment by-products and nanomaterials including metal oxides, zero-valent metals, quantum dots, dendrimers, composites and nanosilver [16].

According to the previous definitions, the products resulting from steel corrosion in marine environment such as biofilms and iron oxides are considered as emerging contaminants.

#### **3. Corrosion**

Corrosion is the spontaneous destruction of metals and alloys caused by chemical, biochemical and electrochemical interactions between materials and their environments. These environments can be humidity, oxygen, inorganic and organic acids, high pressures, temperature, chlorides, etc. During corrosion, metals tend to convert to more thermodynamically stable compounds [17].

#### **4. Zinc electroplating**

Zinc electroplating provides corrosion resistance by acting as a barrier and sacrificial coating. Because zinc is more reactive that steel, the zinc coating corrodes first, protecting the steel substrate. The rate of corrosion of zinc is at least 10 times slower than that of steel, thus a thin coating of zinc can protect steel for long time.

**293**

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

Electroplating is an electrochemical process, which takes place according to a certain number of elementary stages of electrolytic crystallization leading to the reduction of the dissolved species M+n into metal atoms M, and to the incorporation of these atoms into the crystal lattice of the substrate. In general, for a coating, we have to make the cathode the object to be coated, the anode is then made of the metal, which we want to coat and the electrolyte will contain a solution of a salt of this metal. Species to increase electrolyte conductivity and additives are added to improve leveling metal and to optimize the properties of the deposited metal [11].

The development of coatings requires when using a direct current, the addition in small quantities of certain organic or inorganic additives to the electrolysis bath. These additives will modify the mechanisms of electrodeposition by selectively affecting the rate of germination and/or growth of deposited species. The use of additives in electrolysis baths is expressed by a reduction in surface roughness, an increase in hardness and an improvement in both deposits gloss and morphology [6].

The stems and leaves of *Taxus baccata* were harvested in April 2016 in Babor (altitude 2000 m), in little kabylia (northern end of the wilaya of Sétif, in Algeria). The aerial parts were cut into small pieces, they were then subjected to an extraction procedure by maceration in a lukewarm methanol–water mixture (7/3:V/V) for 24 hours. This operation was repeated three times. The various recovered fractions were then combined and evaporated under reduced pressure at a temperature below 70° C until a syrupy residue was obtained. The latter phase was taken up by boiling water, decanting for one nights to eliminate the chlorophyll. The filtered mixture was subjected to liquid–liquid extraction using several solvents separately in a sequence of increasing polarity, starting from dichloromethane (MDE), ethyl acetate (EAE) and n-butanol (BE), where the organic phase was recovered for each solvent. The latter solutions were evaporated to dryness using a rotary evaporator to

The tests were carried out on a mild steel of grade E24–2, having a chemical composition in % by weight (C, 0.17; Mn, 0.6; P, 0.035; S, 0.035; Si, 0.04; Al, 0.02 to 0.05; N, 0.01; Fe remaining). Plates of 2 cm x 6 cm x 0.1 cm in dimension were coated with epoxy resin leaving a single exposure surface. The substrates were plated with a pure zinc (99.91%). Prior to each experiment, the surfaces of all samples were mechanically abraded using different types of silicon carbide emery paper, cleaned with acetone, rinsed with distilled water then dried with air.

The chloride solution for the coating was a mixture of ZnCl2 (65 g/l), KCl (200 g/l), H3BO3 (20 g/l) and different concentrations of *Taxus baccata* extracts

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

**5. Additives**

**6. Experimental**

**6.1 Plant extracts**

obtain the desired extracts [18].

**6.3 Electrodeposition bath**

(1 g/l to 1.6 g/l) [19].

**6.2 Materials**

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

Electroplating is an electrochemical process, which takes place according to a certain number of elementary stages of electrolytic crystallization leading to the reduction of the dissolved species M+n into metal atoms M, and to the incorporation of these atoms into the crystal lattice of the substrate. In general, for a coating, we have to make the cathode the object to be coated, the anode is then made of the metal, which we want to coat and the electrolyte will contain a solution of a salt of this metal. Species to increase electrolyte conductivity and additives are added to improve leveling metal and to optimize the properties of the deposited metal [11].
