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Eco-Friendly Bacterial Strains as Corrosion Inhibitors for Mild Steel in the Red Sea Water

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16 wrz 2025

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Fig. 1a.

Visual images of mild steel specimens after immersion in a) free seawater at different time intervals and b) after 12 weeks of exposure to seawater without and with bacterial inhibitors.
Visual images of mild steel specimens after immersion in a) free seawater at different time intervals and b) after 12 weeks of exposure to seawater without and with bacterial inhibitors.

Fig. 2.

Alteromonas mediterranea isolates a) BAC1, b) BAC2, and c) BAC3. The first description was based on its motility and Gram-negative status. 100×, scale bar = 10 μm.
Alteromonas mediterranea isolates a) BAC1, b) BAC2, and c) BAC3. The first description was based on its motility and Gram-negative status. 100×, scale bar = 10 μm.

Fig. 3.

The agarose gel electrophoresis showing the amplification of 16S rRNA gene from seven bacterial isolates (1 to 7). M – DNA ladder: molecular size marker
The agarose gel electrophoresis showing the amplification of 16S rRNA gene from seven bacterial isolates (1 to 7). M – DNA ladder: molecular size marker

Fig. 4.

The phylogenetic tree was constructed based on the alignment of the 16S rRNA gene sequences of BAC1 (OR852740.1), BAC2 (OR852741.1), and BAC3 (OR852742.1) with other bacterial accessions available in GenBank. The tree was constructed using neighbor-joining (NJ) in CLC Main Workbench V8.1.3 (QIAGEN, Germany). The numerical values at the branch nodes indicate the bootstrap values.
The phylogenetic tree was constructed based on the alignment of the 16S rRNA gene sequences of BAC1 (OR852740.1), BAC2 (OR852741.1), and BAC3 (OR852742.1) with other bacterial accessions available in GenBank. The tree was constructed using neighbor-joining (NJ) in CLC Main Workbench V8.1.3 (QIAGEN, Germany). The numerical values at the branch nodes indicate the bootstrap values.

Fig. 5.

Nyquist plots for mild steel corrosion in seawater in the absence and presence of bacterial inhibitors at a) 1 hour and b) 24 hours of immersion.
Nyquist plots for mild steel corrosion in seawater in the absence and presence of bacterial inhibitors at a) 1 hour and b) 24 hours of immersion.

Fig. 6.

Polarization curves for mild steel corrosion in seawater in the absence and presence of bacterial inhibitors at a) 1 hour and b) 24 hours a of immersion.
Polarization curves for mild steel corrosion in seawater in the absence and presence of bacterial inhibitors at a) 1 hour and b) 24 hours a of immersion.

Corrosion rates and inhibition efficiencies for mild steel corrosion in seawater in the presence of BAC1 (Pseudoalteromonas phenolica) over a 24-week immersion period_

Immersion period (weeks) Weight loss Δw (g) Pit depth Pd (μm) Corrosion rate CRWL (μm y−1) IEWL%
1st 0.0008 ± 0.00003 0.05 ± 0.01 2.64 ± 0.10 92.78 ± 1.1
2nd 0.0016 ± 0.00005 0.12 ± 0.02 3.04 ± 0.12 89.65 ± 1.2
4th 0.0021 ± 0.00007 0.15 ± 0.02 1.95 ± 0.08 93.41 ± 1.0
6th 0.0023 ± 0.00008 0.17 ± 0.02 1.44 ± 0.07 95.08 ± 0.9
9th 0.0029 ± 0.00009 0.21 ± 0.03 1.19 ± 0.05 96.37 ± 0.8
12th 0.0028 ± 0.00008 0.20 ± 0.03 0.86 ± 0.04 92.76 ± 0.7
16th 0.0150 ± 0.0004 1.06 ± 0.05 3.45 ± 0.14 59.74 ± 1.5
24th 0.0255 ± 0.0006 1.66 ± 0.06 3.60 ± 0.15 70.94 ± 1.4

Corrosion rates and inhibition efficiencies for mild steel corrosion in seawater in the presence of BAC 2 (Pseudoalteromonas shioyasakiensis) over a 24-week immersion_

Immersion period (weeks) Weight loss Δw (g) Pit depth Pd (μm) Corrosion rate CRWL (μm y−1) IEWL%
1st 0.0003 ± 0.00001 0.02 ± 0.01 1.11 ± 0.05 96.96 ± 0.9
2nd 0.0010 ± 0.00004 0.09 ± 0.02 2.43 ± 0.10 91.72 ± 1.1
4th 0.0024 ± 0.00006 0.17 ± 0.02 2.26 ± 0.09 92.37 ± 1.0
6th 0.0025 ± 0.00007 0.19 ± 0.02 1.67 ± 0.08 94.28 ± 0.9
9th 0.0027 ± 0.00008 0.19 ± 0.02 1.12 ± 0.05 96.60 ± 0.8
12th 0.0022 ± 0.00007 0.16 ± 0.02 0.69 ± 0.03 94.18 ± 0.7
16th 0.0156 ± 0.0005 1.10 ± 0.05 3.57 ± 0.13 58.27 ± 1.6
24th 0.0228 ± 0.0006 1.62 ± 0.06 3.52 ± 0.14 71.55 ± 1.4

Impedance parameters for corrosion of mild steel in sweater in the absence and presence of bacterial inhibitors_

Medium Time (h) Rs(Ω cm2) Rct (Ω cm2) Cdl (μF cm-2) IER%
Blank 1 3.73 ± 0.08 916.7 ± 35 15.68 ± 0.6
BAC 1 5.31 ± 0.12 8826.0 ± 110 4.48 ± 0.2 89.61 ± 1.2
BAC 2 5.67 ± 0.13 6914.0 ± 95 4.923 ± 0.2 86.74 ± 1.1
BAC 3 3.19 ± 0.09 6128.0 ± 90 5.18 ± 0.2 85.05 ± 1.0
Blank 24 4.51 ± 0.10 631.6 ± 30 20.01 ± 0.7
BAC 1 4.87 ± 0.11 1183.0 ± 45 9.61 ± 0.3 46.61 ± 1.1
BAC 2 5.09 ± 0.12 8112.0 ± 102 2.07 ± 0.1 92.22 ± 1.3
BAC 3 3.45 ± 0.10 1118.0 ± 42 10.25 ± 0.4 43.56 ± 1.0

Polarization parameters for corrosion of mild steel in sweater in the absence and presence of bacterial inhibitors_

Medium Time (h) –Ecorr(mv) βa (mV dec-1) -βc (mV dec-1) icorr (mA cm-2) IEi %
Blank 1 538.4 ± 2.1 80.25 ± 1.5 43.73 ± 1.2 0.3607 ± 0.012
BAC 1 478.7 ± 1.8 70.28 ± 1.2 121.92 ± 1.6 0.0099 ± 0.0004 97.25 ± 0.8
BAC 2 449.1 ±1.7 84.28 ± 1.4 155.09 ± 1.7 0.0097 ± 0.0003 97.31 ± 0.9
BAC 3 429.2 ± 1.6 92.80 ± 1.4 97.73 ± 1.4 0.0081 ± 0.0003 97.75 ± 0.9
Blank 24 524.1 ± 2.0 54.64 ± 1.3 57.39 ± 1.3 0.4991 ± 0.015
BAC 1 405.0 ± 1.9 62.54 ± 1.1 123.19 ± 1.5 0.0229 ± 0.0006 95.41 ± 0.7
BAC 2 449.5 ± 1.8 97.49 ± 1.6 150.68 ± 1.6 0.0189 ± 0.0005 96.21 ± 0.8
BAC 3 566.3 ± 2.2 94.02 ± 1.5 80.17 ± 1.3 0.1868 ± 0.006 62.57 ± 1.2

Corrosion rates and inhibition efficiencies for mild steel corrosion in seawater in the presence of BAC 3 (Alteromonas mediterranea) over a 24-week immersion period_

Immersion period (weeks) Weight loss Δw (g) Pit depth Pd (μm) Corrosion rate CRWL (μm y−1) IEWL%
1st 0.0001 ± 0.00001 0.007 ± 0.01 0.36 ± 0.02 99.00 ± 0.5
2nd 0.0009 ± 0.00003 0.07 ± 0.02 1.74 ± 0.08 94.06 ± 0.9
4th 0.0017 ± 0.00006 0.12 ± 0.02 1.60 ± 0.07 94.59 ± 0.8
6th 0.0027 ± 0.00007 0.18 ± 0.03 1.56 ± 0.07 94.65 ± 0.8
9th 0.0036 ± 0.00008 0.26 ± 0. 03 1.52 ± 0.06 95.39 ± 0.7
12th 0.0038 ± 0.00009 0.27 ±0.04 1.18 ± 0.05 90.11 ± 0.6
16th 0.0159 ± 0.0005 1.16 ± 0.05 3.80 ± 0.15 55.65 ± 1.8
24th 0.0786 ± 0.0012 5.44 ± 0.10 11.82 ± 0.30 4.57 ± 2.0

Information and identification for 16S rRNA gene sequences of BAC1, BAC 2, and BAC 3_

Code Reference accession numbers Identified bacterial isolates Identity %
BAC 1 (OR852740.1) NR 113299.1 Pseudoalteromonas phenolica 99.42%
NR 028809.1 Pseudoalteromonas phenolica 98.27%
KY073271 Pseudoalteromonas phenolica 99.80%
BAC 2 (OR852741.1) NR 125458.1 Pseudoalteromonas shioyasakiensis 96.67%
BAC 3 (OR852743.1) NR 148755.1 Alteromonas mediterranea 98.17%
NR 148756.1 Alteromonas mediterranea 98.46%

Pit depth and corrosion rates of mild steel control at different immersion time in seawater_

Immersion period (weeks) Weight loss Δw (g) Pit depth Pd (μm) Corrosion rate CRWL (μm y−1)
1st 0.0097 ± 0.0006 0.70 ± 0.03 36.54 ± 1.12
2nd 0.0161 ± 0.0011 1.13 ± 0.05 29.37 ± 0.94
4th 0.0311 ± 0.0018 2.27 ± 0.07 29.55 ± 0.97
6th 0.0484 ± 0.0024 3.36 ± 0.09 29.19 ± 1.03
9th 0.0820 ± 0.0031 5.68 ± 0.12 32.93 ± 1.22
12th 0.0398 ± 0.0042 2.75 ± 0.10 11.95 ± 0.81
16th 0.0368 ± 0.0054 2.63 ± 0.09 8.56 ± 0.63
24th 0.0789 ± 0.0079 5.70 ± 0.14 12.38 ± 0.77

Chemical analysis of Red Sea water sample_

Parameter Value Unit
Salt-related ions
Ca2+ 496.0 mg/l
Mg2+ 1,512.0
Na+ 11,920.0
K+ 588.0
Cl 22,336.0
HCO3 156.0
NO3 1.0
SO43– 2,440.0
PO3 < 0.1
CO32– < 0.1
SiO2 < 1.0
Other Parameters
Total dissolved solid (TDS) 43,550.0 mg/l
Total suspended solids (TSS) < 5.0 mg/l
Total alkalinity 128.0 mg/l as CaCO3
pH 8.1
Conductivity 72,550.0 μS/cm2
Język:
Angielski
Częstotliwość wydawania:
4 razy w roku
Dziedziny czasopisma:
Nauki biologiczne, Mikrobiologia i wirusologia