Deterioration of glass surfaces and facades

Water and surface corrosion to glass, invisible as it may seem, degrades the surface of glass and over time will become more and more noticeable. New solutions using advanced hydrophobic glass coating allow protecting these surfaces, making them self-cleaning to some degree and keeping the glass looking newer for longer.

Glass surface corrosion

New glass is bright and sparkling, easy to see through and easy to clean and keep clean. Contrary to popular belief, the surface of the glass is not completely smooth. It has what glass manufacturers call 'lattice' or 'honeycomb' patterns. Under a microscope glass reveals a rougher surface made of peaks and potholes. Organic and inorganic contaminants fill these potholes and react chemically with the glass, firmly bonding to its surface. As a result, glass easily becomes stained and discoloured, difficult to see through and difficult to clean and keep clean. The surface of the glass also possesses hydrophilic (water attracting) properties and over time is subjected to a corrosion process that will make its surface rougher and therefore its damage greater, in some cases irreversibly so.

Glass is more resistant to corrosion than most materials, so much so that it is easy to think of it as almost corrosion-proof. However glass windows after several years’ exposure to the elements do  not always remain clear and unaffected. This has great implications on the property owner and any other users of glass, increased costs and efforts in maintenance, renovation or replacement, and in all cases a reduction in the expected performance.

Just as metal rusts, glass is subjected to a corrosion process caused by reactions between the glass surface and gases in the atmosphere. It is commonly associated with moisture or vapour attack through condensation, or reaction with an alkaline solution.

Glass naturally attracts water (i.e. is hydrophilic), meaning it attracts and holds moisture. All glass has a molecular layer of moisture on the surface. When this layer increases because of humidity or rainfall, it can obscure visibility and create a risk to comfort or safety. But most of all, it participates greatly to the destruction of the surface of the glass.

Corrosion by water

Corrosion by water is similar to acid corrosion in that alkali is removed from the glass surface. Water corrosion acts at a much slower rate. There are two distinct stages to the corrosion process, occurring together or separately. The first stage is aqueous corrosion, caused by moisture. It is referred to as ion exchange or alkali extraction (leaching). An ion exchange occurs between sodium ions from the glass and hydrogen ions from the corrosion solution. The remaining components of the glass are not altered, but the effective surface area in contact with the solution is increased. This increase in surface area leads to extraction or leaching of the alkali ions from the glass, leaving a silica-rich layer on the surface. As silica (SiO2) concentration in the glass goes down, surface area increases through dissolution of the glass surface. The pH of the solution in contact with the glass will greatly affect the corrosion process. A rapid pH increase will cause a rapid breakdown of the glass surface.

Unprotected glass

Ordinary, unprotected glass is not hygienic. An alternative to using potentially hazardous chemical disinfectants is frequent and intensive washing with water and detergents. However, this approach is high-maintenance, labour-intensive and, if the use of detergents and water consumption is not controlled, cannot be considered as either green or hygienic.

It is difficult – sometimes impossible – to clean, keep clean and disinfect ordinary glass. Even when new, glass is microscopically rough with countless places for bacteria to hide and multiply. With exposure to alkalinity from industrial cleaning products and moisture, both liquid and vapour, the surface of unprotected glass becomes corroded and even rougher. Also, unprotected glass chemically reacts with contaminants, such as hard water deposits, which bond firmly to glass – making it even more difficult to clean, keep clean and disinfect.

Advances in glass protection

Glass usage in the country has been growing dramatically over the past decade. We all like our houses and buildings to open up to the environment and be flooded with natural light. Architects and decorators are innovatively using glass for a variety of applications from skylights to partitions, balustrades to staircases, and many-many more that make our surroundings look more spacious and beautiful. In this past, this has led to a trade off with safety, security, energy efficiency, and noise insulation.

Glass is more than functional; it is architectural. It gives the illusion of more space, increases natural lighting, and lends character to interior spaces. Architectural glass goes beyond architecture to become art, using textures, patterns, colours, and technique to define and highlight individual tastes.

Whichever glass you speak about, without surface protection it will always be left exposed to the natural elements and invariably corrode or degrade.

Glass protection in the form of silica based coatings is becoming more and more popular and readily available creating a sort of “self cleaning” face that protects the glass from corrosive elements plus turns the natural hydrophilic face of glass to hydrophobic, making it water repellent and causing water drops to “curl” up and run off, rather than spreading out and depositing in the invisible rough face of glass.