1. HOW LONG DOES IT TAKE TO GALVANIZE?
There is a perception that hot dip galvanizing is a very time consuming process. Actually, the process of dipping steel in molten zinc takes just a matter of minutes. What takes a bit longer is the preparation beforehand. The steel must be hung on jigs, cleaned, rinsed and fluxed before it can be galvanized. Afterwards, it must cool and be taken off the jigs. The time to do all of this is only a few hours. Remember, there is a lot of other work being processed too - so the typical turnaround time is about three days. By arrangement it may even be possible to do it in 24 hours.
2. WHAT CAN I DO TO MINIMIZE TURNAROUND TIME?
First, ask our customer service representative about his workload. By phoning a few days beforehand your work can be planned into his schedule. Click here for plant information.
Second, send in "clean" steelwork. Work that is contaminated with material which will not be removed by the normal galvanizing pre-treatment will need special steps to remove it, which takes time. So remove paint or grease, before the steelwork is sent to be galvanized. (Rust is not a problem, but the more there is, the longer it will take to remove).
Third, put the correct vent and drain holes in hollow steelwork. Holes are essential for safe and effective galvanizing - it takes extra time if we have to put them in. For more information on proper venting / draining, please refer to question #7 below.
Fourth, allow for transport time. If we are providing transport, please liaise with our shipping department about our regular runs and plan around them.
3. HOW LARGE (OR SMALL) CAN I FAB IT?
By designing and fabricating in sections suitable for our galvanizing facilities, almost any component can be galvanized. When an item is too large for total immersion in the kettle but more than half of the item will fit into the kettle, the piece may be "double dipped". Please verify the kettle constraints with us at an early stage. Please visit kettle dimensions.
Small items receive special attention during galvanizing. Pieces such as fasteners, small brackets and clips are galvanized in perforated baskets. The basket is then centrifuged to throw off excess zinc, delivering smoother coatings.
4. WHAT CAN I DO TO ENSURE I RECEIVE THE HIGHEST-QUALITY GALVANIZED COATING?
Three-way consultation among the designer, fabricator and galvanizer is key to Pure Metal's enviable record of customer satisfaction. Ongoing communication can optimize turnaround time, minimize cost, and ensure superior quality hot-dip galvanized steel. To better appreciate the design considerations for hot-dip galvanizing, it helps to understand the basic steps of the galvanizing process. Please click here for the fundamental steps.
5. CAN YOU HOT DIP CASTINGS AND FORGED PARTS?
Certainly! However, our cleaning processes do not clean castings well because sand and other surface inclusions are not removed by the cleaning solutions. Thorough abrasive cleaning is the most effective method for removing foundry sand and impurities. This is conventionally accomplished by abrasive blasting. Grit-blasting or a combination of grit and shot generally is preferred.
For information on abrasive blasting facilities, please visit www.blastal.com and www.blastech.com.
6. WHAT ARE THE GUIDELINES FOR OVERTAPPING NUTS & INTERIOR THREADS?
While bolts are completely galvanized, internal threads on nuts must be tapped oversize after galvanizing to accommodate the increased diameter of the bolts. The specification and recommended overtapping for Carbon and Alloy Steel nuts and interior threads is defined in detailed in ASTM A 563, Specification for Carbon and Alloy Steel Nuts: Click here.
7. WHY ARE HOLES REQUIRED TO GALVANIZE CLOSED-OFF HOLLOW SECTIONS?
It is important to bear in mind that the steelwork is immersed into and withdrawn from a bath of molten zinc at about 450 degrees Celsius (840 degrees Fahrenheit.) Any features that aid the access and drainage of molten zinc will improve the quality of the coating and reduce costs. For complete protection, molten zinc must be able to flow freely to all surfaces of a fabrication. With hollow sections, or where there are internal compartments, the galvanizing of the internal surfaces eliminates any danger of hidden corrosion during service.
8. ARE THE RESULTS FROM SALT SPRAY TESTING RELIABLE WHEN PREDICTING THE LIFESPAN OF A ZINC COATING?
Actually, the results from salt spray tests can be misleading and may predict a much shorter life for a hot dip galvanized coating than in reality.
The development of a patina on the surface of a galvanized coating provides a very corrosion resistant surface due to its very low solubility. This basic zinc carbonate layer develops slowly over a number of months. In accelerated tests, such as salt spray, the protective patina does not have the opportunity to develop so the tests predict a much shorter life for the coating.
9. WHAT DOES IT COST TO ZINC "HOT DIP" GALVANIZE?
As shown in the chart below, the zinc "hot dip" process costs far less than other protective coating methods having much shorter maintenance free lives.