Contents lists available at ScienceDirect Progress in Organic Coatings journal homepage: www.elsevier.com/locate/porgcoat One pot fabrication of superhydrophobic anticorrosive coating without fluoro compounds and inhibitive pigments C. Anitha a,c , S. Syed Azim a,c , S. Arunkumar b , Sundar Mayavan b,c, ⁎ a Corrosion and Materials Protection Division, CSIR – Central Electrochemical Research Institute, Karaikudi, India b Lead Acid Battery Section, CSIR – Central Electrochemical Research Institute, Karaikudi, India c Academy of Scientific and Innovative Research, New Delhi, India ARTICLE INFO Keywords: Fluorine free Superhydrophobic Corrosion protection Silicone binder ABSTRACT We report the successful fabrication of fluorine free superhydrophobic coating involving silicone binder, pig- ments like nanosilica, nanotitania and magnesium silicate and aluminium stearate as additive. The pristine resin with no pigments and additives show hydrophobic behaviour with water contact angle (WCA) of 93.5° and tilting angle (TA) of 60°. The WCA increased to 152.5° and TA to 20° with incorporation of pigments and additives. The introduction of pigments/additives created micro/nano roughness through agglomeration of pigments used in the coating. The as prepared superhydrophobic coating also exhibited excellent corrosion resistance property without using any inhibitive / sacrificial pigments in it. To the best of our knowledge this is the first work towards preparation of superhydrophobic coating with excellent corrosion protection without fluoro compounds and inhibitive pigments. 1. Introduction Superhydrophobicity is a state at which the surface emanates ex- treme water repellency over which water droplets attain spherical shape and the contact angle (CA) exceeds 150° with low contact angle hysteresis (CAH). [1] Wetting phenomenon is accustomed in many in- dustrial processes and plays a crucial role in many processes like coating, heat transfer, pesticide application and cleaning [2,3]. The basic equation for wetting phenomenon dates back 200 years which was formulated by Young [4]. The degree of wetting by a liquid is re- flected in the CA it makes with the solid surface. CA of water on the solid surface is entailed by the specific surface energies of solid – gas, liquid – gas and solid – liquid interfaces. CA relies on the surface chemistry and surface roughness of the solid surface. The limiting factor for chemical hydrophobicity is circumscribed to 120° and it cannot be outnumbered without substantial surface roughness. [5–7] Surface roughness has a profound influence on wetting. Superhydrophobicity culminates when the hydrophobicity of a substrate is amplified by roughness [8].Therefore, superhydrophobic surfaces always possess appropriate surface roughness at micro/nanometer scale. With their unparalleled properties and growing demand super- hydrophobic surface is an active area of research for the past few decades. Diversified approaches have been made so far, to fabricate superhydrophobic surfaces using a vast number of materials over a wide number of surfaces. Most methods involve strict and harsh che- mical treatment, sophisticated and time consuming processing proce- dures and expensive materials. There is thrive for the development of simple, nontoxic, economically affordable and viable application pro- cedure and chemical method to fabricate superhydrophobic surfaces for practical use over a large surface area. Coating provides an efficient platform for scaling up superhydrophobic surfaces and it is more ad- vantageous than many other methods. It is more practical, convenient, inexpensive and easy to apply in large scale. Traditionally, coating comprise of binder, pigment, additives and solvent. Depending on the coating thickness we need to build, volume solids (VS) and pigment volume concentration (PVC) are fixed. VS is the amount of non-volatile solids left after drying/curing of the coating which includes resin, pigment and additive and PVC is the ratio of the volume of pigment to the total VS. Based on the refractive index (RI) pigments are classified as main pigments and extender pigments. The role of main pigment is to provide hiding to the coating which should have a RI ≥ 3.7. Extender pigments are comparatively less expensive than main pigment which are used to bring down the cost and to alter the properties of the coating. Mostly, superhydrophobic coating is prepared from fluorinated polymers or polydimethylsiloxane (PDMS). The intrinsic low surface energy of fluorinated polymers [9,10] and PDMS [11] generate super- hydrophobicity readily but they have many disadvantages in terms of https://doi.org/10.1016/j.porgcoat.2018.09.003 Received 23 March 2018; Received in revised form 9 August 2018; Accepted 1 September 2018 ⁎ Corresponding author. E-mail addresses: anithachemi16@gmail.com (C. Anitha), azimcecri@gmail.com (S.S. Azim), sundarmayavan@cecri.res.in (S. Mayavan). Progress in Organic Coatings 125 (2018) 137–145 0300-9440/ © 2018 Elsevier B.V. All rights reserved. T