# Properties of the Iron Bacteria Biofouling on Ni-P-rGO Coating
## 1 Introduction  
Biofouling is a biofilm or an organic film that is formed by bacteria, algae, and other microorganisms, as well as their exceta that are deposited on a solid surface [1]. Biofouling can lead to severe issues, such as decreased heat transfer efficiency, corroded materials, and even safety accidents, when present on the surfaces of heat exchangers, water distribution pipes, cooling towers, and other structures [2]. Currently, modified surfaces have been widely used in various industries because of their anti-fouling, anti-corrosion, and non-pollution properties. In the last twenty years, multiple studies have focused on the anti-bifouling properties of modified surfaces. [PERSON] and [PERSON]. [3] found that a coating of Ni-P-poly tetrafluoroethylene (Ni-P-PTFE) with a surface energy in the 21-26 mJ/m\({}^{2}\) range exhibited an excellent antimicrobial property and reduced the _Escherichia (XA90)_ adhesion by 95% compared with stainless steel 304. [PERSON] et al. [4] and [PERSON] et al. [5] studied the effect of electroless Ni-P and Ni-Cu-P coatings on the biofouling of iron bacteria, respectively, and they demonstrated that Ni-P and Ni-Cu-P coatings have excellent anti-fouling properties. [PERSON] et al. [6] found that a silver coating could inhibit the attachment of _Pseudomonas aeruginosa (PA01)_. Recently, the efficiency of the coating materials has been improved; the addition of carbon materials into the Ni-P electroless plating solution has been shown to lead to a coating material with good wear resistance, corrosion resistance, and anti-fouling. [PERSON] et al. [7] showed that an Ni-P-graphene oxide (Ni-P-GO) coating on a mild steel surface possessed the best anti-wear and microhardness properties when 40 mg/L of graphene oxide was added into an electroless plating solution. [PERSON] et al. [8] prepared a modified diamond-like carbon (DLC) coating that reduced the adhesion of an aluminumsilicate deposit by 97% compared with uncoated stainless steel. [PERSON] et al. [9] added graphene oxide to reinforce an Ni-P coating material to inhibit the adhesion of _Staphylococcus aureus_. Graphene has been increasingly used as a carbon material because of its outstanding thermal conductivity, stability, and reduced dispersion. Though the dispersion of graphene is low, several studies have still prepared Ni-P-reduced graphene oxide (Ni-P-rGO) coatings via electroless plating. [PERSON] et al. [10] fabricated graphene-enhanced Ni-P composite films and found that the G-Ni-P composite plating increased Vickers' hardness and Young's modulus values compared to an Ni-P coating. [PERSON] et al. [11] prepared an Ni-P-diamond/graphene coating; the coating exhibited increased hardness, corrosion resistance, and wear resistance in a 3.5 wt % NaCl solution compared with Ni-P/diamond and Ni-P/graphene coatings. However, limited work has been carried out on the inhibition of the biofouling of Ni-P-rGO coatings. Though the application of a modified surface can decrease biofouling, the reaction mechanism has not yet been fully explored; furthermore, contradictive theses on the reaction mechanism are available in the literature. [PERSON] et al. [12] demonstrated that low-energy substrates attracted reduced numbers of marine bacteria, while high-energy substrates led to an increased presence of bacteria. [PERSON] [13] proposed an optimal surface energy for decreasing biofouling. However, according to other studies, decreased biofouling could be detected on high-energy surfaces, with high-energy surfaces exhibiting a higher removal rate than low-energy surfaces. [14, 15]. [PERSON] et al. [16] reported that there was no significant relationship between surface energy and bacterial adhesion. Nowadays, more and more researchers are explaining the phenomenon through the idea that modified surfaces decrease biofouling via the extended DLVO theory [17, 18, 19, 20, 21, 22], which is a theory of colloidal stability.