Coatings for Galvanized Structures

Galvanized structures often need to be coated and repaired in the field, because the service conditions are such that the zinc layer will not be able to form the familiar patina and thus will self-sacrifice prematurely. Examples include marine environments or embedded or ground-level service. On older structures, the zinc may be damaged or simply depleted. The application of a coating over zinc (which is, in its own right, a kind of coating) is commonly called “duplex painting”.

In 2008, GemThane developed a new alternative for its customers who wish to coat galvanized structures in the field. Historically, the ideal surface preparation has been abrasive blasting; however, in the field this has not always been possible. As a result, a more practical approach, such as hand and power tool cleaning, is often used at the expense of long-term performance. Hand tool cleaning is also labor-intensive.

It used to be that, in order to achieve the best long term results with duplex painting, nothing matched the performance of abrasive blasting. The invention of GemBond in 2007 has changed all that with a simple, elegant, effective, and economical alternative to blasting.

GemBond is GemThane’s unique Surface Conditioner that eliminates the need for aggressive blasting. This environmentally-friendly, soap-like compound is simply brushed or sprayed onto the metal surface. In about twenty minutes, it dissolves oxidation, removes contaminants, and lays down a layer of Madison’s exclusive AP-50 Adhesion Promoter. After the “spent” GemBond is washed away with ordinary hot tap water, and the structure is thoroughly dried, the surface is ready to coat.

There is a choice of several topcoats, each of which contains the same AP-50 Adhesion Promoter. They work synergistically over the GemBond-prepared surface to provide adhesion comparable to a costly grit blast.

The variety of available topcoats includes Liquid Metal, OverCote, and 1:4 Aliphatic, among others. The three we have mentioned are self-priming and user-friendly for field applications, using rollers, brushes, or airless spray. Some topcoats are available with different catalysts to meet your specific cure time requirements. Most GemThane topcoats may also be applied at cool temperatures, extending the coating season in northern climates.