Becoming a Protective Coating Expert
Hydrophobic Coatings vs. Hydrophilic Coatings
(Had been called “Self-Cleaning Coating”)
|Meaning||water-fearing, repels liquid from the surface||attract the water to the surface|
|Liquid (ie. Water Droplets)||Bead up||Sit flat|
Hydrophobic literally means "water-fearing". When we use the term hydrophobic we are talking about a surface that is trying to repel the liquid away from it. This is the type of coating that DFI creates with most of its liquid and vapor protective coatings.
On the other hand, Hydrophilic coatings attract the water to the surface and make the water sit flat instead of “beading up” as the hydrophobic coatings do. While these coatings are in effect doing the exact opposite thing to each other the funny thing is they are both used to create low maintenance surfaces.
So how do they compare to each other? Hydrophobic coatings’ advantages are that they create more clarity, more impact and scratch resistance, and can be applied with much greater industrial flexibility (i.e. in many different simple methods including in the field). Less water on the glass also means less mold and mildew and less calcium and mineral leaching.
On the other hand, hydrophilic coatings, which in the past have been called "self-cleaning coating", is a photo-catalyst nano-particle coating that creates an oxidizing effect on organic dirt and contaminants that come in contact with it as long as the glass is in sunlight. This oxidation loosens the dirt and converts it in many cases so that when there is rain or a manual washing much of the dirt may rinse off. The main drawbacks of this method are the waviness in appearance of the glass when water is present, the lack of impact or scratch resistance, in fact in many cases hydrophilic easier to scratch than untreated glass. Also all hydrophilic glass from the major manufacturers like PPG Guardian and Pilkington cannot be repaired or manufactured in the field making it an expensive proposition when it doesn't work properly.
In the case of this "self-cleaning glass" a few years ago Consumer Reports looked into it and found that the product did not meet the muster of its reviewers. One key reason for not passing their tests was the problem of not staying clean without rain or manual rinsing and the requirement for these hydrophilic coatings to have adequate sunlight to activate their photo catalyst activity. For example, if they were in the shade they don't work well.
For most glazing applications, hydrophobic coatings like those Diamon-Fusion International (DFI) manufactures will provide greater value, performance, and durability.