Hot-dipped Galvanizing is an in-depth process whereby the steel is primed, removing excess mill scaling, dirt, and debris that accumulates on the metal including any rust particulates that have accumulated on the surface. This accumulation of particulates on the surface is known as the surface profile. NACE International and the Society of Protective Coatings, as well as, the ASTM International Standard (American Society for Testing and Materials) offer further information on the acceptable standardized practices.
Once the blasting has applied, the material is then hung on rod or wire and then dipped into a large "vat" of molten zinc heated to a temperature between 815⁰ - 850⁰. Once immersed, the zinc reacts with the chemical composition of the steel iron alloy creating a metallurgically bonded zinc-iron alloy layer forming a final top coat that is 100% zinc.
In areas like Florida, that has climatic conditions that can cause erosion and rust to form due to the moisture and sea air galvanizing steel is a cost-effective way to substitute Stainless Steel and other corrosion-resistant metals that are costlier. Mainly, Marina's and coastal areas where the corrosive elements of the salt water and air can destroy steel quickly, by applying the zinc coat to your steel you avoid costly repairs and replacements down the road. For example, a beam hot dipped galvanized can have an average life expectancy of between 15-30 years; however, when exposed to salt air or spray, the life span is about half that. When looking for material such as corrugated roofing or B-deck, for example, the specs are typically given a G-code of either G60 or G90. The higher the code, the longer the life span.
As mentioned in our previous blog, Blast and Prime, we discussed that sometimes your plans would call for a blast and prime, galvanized and the primed to a Safety Yellow. While under ordinary circumstances this might be a bit of overkill, some projects require the added process of priming after galvanization. If you are working with FDOT, it is critical to note that the process of quenching is eliminated during the galvanization process so that you can prime or powder coat as necessary on your galvanized material. Quenching is the process whereby the galvanized metal is water quenched in a solution of potassium dichromate which then applies a chromate finish to the zinc covered surface. By eliminating this process, you can then proceed to prime or powder coat to the required color.
Cold-dipped or spray on Cold Galvanizer
Cold galvanizer is available in gallons or spray cans, and you can find these at your local big box store. According to the to eh AGA (American Galvanizers Association) the process of cold galvanizing is a matter of painting or spray-on use of a cold galvanizer. Because it does not have the same zinc content that is used in hot-dipped. It will also provide you the longevity that hot-dipped does, however in a pinch to touch up something that has experienced wear over time; it is a great way to solve a minor problem cost-effectively. If you have a project and the wear over time is not a factor, a paint or spray on cold galvanizer will do the trick. *
*It is imperative to note that when applying any zinc-rich coating, do it in a well-ventilated environment, or outside and you want to wear safety gear such as a breathing mask and gloves. Also, when applying a cold galvanizer, it is usually recommended that you use two coats and allow plenty of time (24-48 hrs each coat) between coats for more extended wear and better coating.
Regardless of your needs, Spirit Metals is prepared to provide you a comprehensive quote to your specific needs. Our primary goal is to understand the needs of your business, your project, and your budget. At Spirit, we partner with you to achieve those goals. Contact us today, and one of our dedicated team members will assist you!