Anticorrosion/antifouling properties of bacterial spore-loaded sol–gel type coating for mild steel in saline marine condition: a case of thermophilic strain of Bacillus licheniformis

Abstract

This work reports the performance of a sol-gel type coating encapsulated with biofilm of inoculums of protective thermophilic strain of Bacillus licheniformis endospores isolated from the Gazan hot springs-Saudi Arabia for the inhibition of marine fouling and corrosion protection of S36-grade mild steel in 3.5 wt% NaCl medium. In order to improve its anticorrosion properties, the hybrid sol-gel coating is further doped with zinc molybdate (MOLY) and zinc aluminum polyphosphate (ZAPP) pigments. Marine fouling study was conducted at the Arabia Gulf water of Half Moon Bay, Al-Khobar, Saudi Arabia for 10 weeks on the coated samples with and without the bacterial endospores. The assessment of fouling results reveals that the bacterial endospores possess antifouling potentials since it performed better compared to its abiotic counterpart within the immersion period of study due to their foul-releasing effect. Improved corrosion and fouling resistant in the presence of the bacterial endospores could be attributed to their multi-layered hydrophobic and antibiotic coating surface after bacterial encapsulation. Spores accumulation in the sol-gel coating altered the surface wetness thereby preventing the diffusion of corrosion molecules and ions through the bulk of the coating to the metal surface; this is evident in the trend of electrochemical coating resistance and capacitance. Confocal laser scanning fluorescence and scanning electron microscopies were employed to probe bacterial viability and surface micro-cracks inherent in the coating, respectively. This is the first report of axenic thermophilic strain of Bacillus licheniformis isolated from the Arabian Gulf with inhibiting potentials against corrosion and fouling of industrial steel.

Hybrid organosiloxane coatings containing epoxide precursors for protecting mild steel against corrosion in a saline medium

“…The hydrophobicity of the coated samples is considered as one of the contributing parameters to the barrier properties of the coating and ultimately its anticorrosion performance . The degree of hydrophobicity of surfaces can be determined using aqueous contact angle testing.…”

Hybrid organosiloxane material/metal oxide composite as efficient anticorrosive coatings for mild steel in a saline medium

“…The corrosion protection performances of the metal oxideembedded hybrid-coated samples were furtherly assessed and compared using the EIS technique; one of the most sophisticated, informative, and routinely used technique in characterizing the protection efficiency of all type of coatings. 7,8,26 The technique can detect any changes occurred on the surface of coated metals even after short times of exposure to the electrolytic solution. Interestingly, the samples FT-Al, FT-Ca, and FT-Zn had high impedance values (>10 9 X) indicating considerable barrier properties after such a relatively long exposure time.…”

Bacillus pumilus Marinos Inhibidores de la Fijación de Microalgas a Sustratos Artificiales

“…Nuevamente se reafirma la potencialidad antibacteriana reportada para B. pumilus C32-MESO por Leyton et al, (2012 Korenblum et al, (2012) indicó que producen sustancias que inhiben bacterias reduc toras de sulfato responsables de la biocorrosión en la industria petrolera. Otra especie de este género como Bacillus lincheniformis han demostrado potencialidad antiincrustantes y anticorrosivas, estas propiedades se pueden atribuir a que las endosporas mejoran la hidrofobicidad alterando la humedad de la superficie e impidiendo la difusión de moléculas/iones de la corrosión a través del revestimiento de la superficie de metal, como también a la acción como antibiótico de las esporas después de la encapsul ación bacteriana (Eduok et al, 2015). La mezcla de bacteria presentó una significativa inhibición de la fijación a los sustratos del Mix UA, incluso la actividad se potenció aún más que cuando se evaluó la fijación de las bacterias por separado.…”