Definition - What does Hydrophobic mean?

Hydrophobic is a property of a substance that repels water. It means lacking affinity for water, and tending to repel or not to absorb water. Hydrophobic molecules tend to be non-polar molecules and group together. Oils and fats are hydrophobic.

Hydrophobic materials often do not dissolve in water or in any solution that contains a largely aqueous environment. Hydrophobic materials are often used to remove oil from water, manage oil spills, and chemical separation processes that require the removal of non-polar substances from polar compounds.

Hydrophobic surfaces decrease corrosion rates, and therefore are used in corrosion resistance.

The opposite of hydrophobic is hydrophilic, water-loving. Surface-active agents contain both hydrophobic and hydrophilic groups on the same molecules.

Corrosionpedia explains Hydrophobic

Hydrophobic refers to substances that cannot dissolve in water. Chemical groups that tend to make substances hydrophobic include -CH2- chains and rings (hydrocarbons). These substances lack the ability to hydrogen bond and their surface free energy is relatively low. Water does not tend to wet hydrophobic surfaces; rather, the droplets stay beaded up with high values of contact angle.

Hydrophobic molecules called hydrophobes repel bodies of water and, owing to the fact that hydrophobes are non-polar, they attract other neutral molecules and non-polar solvents. Natural hydrophobes include alkanes, fats and oils.

Hydrophobic and super-hydrophobic materials possess a set of unique functional properties, namely:

  • Water proof
  • Corrosion resistant
  • Stable against biofouling and inorganic and organic pollutants
  • Ease of fluid flow near hydrophobic surfaces

Material scientists have been working on using various chemicals to alter the surface properties of surfaces to make them hydrophobic. To provide glass with a hydrophobic characteristic, silanes are often used. Similar hydrophobicity concepts have been applied in paints, coatings and textiles.

For example, the super-hydrophobic coatings on 316L stainless steel exhibit an excellent corrosion resistance in chloride-containing solution at room temperature. Corrosion can be protected by making the surface hydrophobic, it is found hydrophobic surfaces strongly decrease the corrosion rate of concrete surface. Hydrophobic surfaces are also important in protecting surfaces from water damage and stains.

Hydrophobic coatings used mainly in sealed environments which are not exposed to wear or cleaning, such as electronic components and air conditioning heat transfer fins, to protect from moisture and prevent corrosion.

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