Chemical glasses and glass coatings for chemical apparatus characteristically have superior acid resistance. This is due to their acidic components and structure. For this reason, acid resistance is their major field of application.

Alkali resistance is usually the inherent advantage of metallic and polymeric vessel materials and defines their principal application range.

However decades of Pfaudler research and development have finally broken down these boundaries.

GMM Pfaudler Standard Glass Coatings

GMM Pfaudler's standard glass coatings already have relatively high alkali resistance without compromising their extremely high acid resistance. They are ideal for conventional glass coating applications and are preferred for highly acid operations with occasional neutralization and intermediate alkaline operations.

Type 4300 Glass Coatings

Type 4300 ® glass coatings represent a new aspect of this tradition and are designed to bridge a perceived gap in the application range. GMM Pfaudler Type 4300 ® glass is still an acidic type of glass, but its primary application is based on improved alkali resistance. Type 4300 glass coatings are advisable wherever alkaline conditions prevail during the cycle, or as a result of concentration and temperature, or where concentration and/or temperature conditions exceed permissible limits for conventional glass.

In addition, Type 4300 ® glass coatings are advisable where any of the following conditions exist:

	Protection of alkaline products against metal contamination.
	Danger of discoloration of alkaline products due to incorporation of metals.
	Stabilization of high-molecular alkalis sensitive to metal contact.
	Inadequate redox stability of the vessel material in the alkaline range.

Compared to our world renowned standard glass, Type 4300 ® has three times better alkali resistance. This means that higher process temperatures can be used, or that, under otherwise equal conditions, these glass coatings will have three times the life expectations.

The Type 4300 ® glass does make a slight concession in the area of acid resistance. Although it is adequate for mild service, it is not recommended for aggressive acid conditions.

Corrosion Resistance

For pure acids and bases most commonly used in the chemical industry , technically relevant parameters influencing the rate of corrosion (for example, the volume/surface area ratio, inhibition effects, concentration, and temperature) are considered.

In practical operation these materials are always encountered with liquid additives, dissolved substances or gases which may have positive or negative effects on resistance. We therefore recommend performing corrosion tests or contacting a Pfaudler consultant to assure material suitability for individual processes.