WHY GALVANIZE?
Due to the strength of the metallurgical bond, along with its ability to withstand very aggressive handling, galvanized coatings continue to be unmatched to date.
The metal is first cleaned, and then the zinc is adhered to the steel using heat as a catalyst. Zinc, unlike other surface coatings, will form a metallurgic bond to the steel, outperforming any other mechanically bonded coating system on the market. Once coated, the zinc will corrode preferentially to the steel using what is called “cathodic” or “galvanic protection”, so that over time, if a scratch appears on the surface, the zinc will react to the elements before the steel will be affected. Bare metal up to one-quarter inch will also be protected by the bonded zinc immediately adjacent to the bare area.
PROCESS
01.
Caustic Cleaning
Similar to hot soap, the alkaline mixture dissolves and removes grease and some paints commonly used in the rolling and fabrication process.
02.
Acid Cleaning
Sulfuric acid is used to remove any rust, mill scale, or any other metallic impurity. Once completed, this process leaves the steel chemically clean and ready to allow the galvanizing reaction to take place. Three 7800-imperial gallon acid pickle tanks provide adequate pickling capacity to meet our customers’ requirements.
03.
Flux
The final step in steel preparation, fluxing, safeguards the steel against premature oxidization, which would otherwise allow rust formation and other surface contamination. This contamination, if allowed to occur, would greatly impede or even halt the galvanizing reaction.
04.
Galvanizing
Lowering the material into liquid zinc will cause the steel to rise in temperature, matching that of the zinc bath. This temperature, sufficient enough to act as a catalyst, initiates the galvanizing reaction. Once complete, the material is slowly withdrawn from the zinc kettle, allowing the excess zinc to drain, leaving a properly galvanized product. At Red River Galvanizing Inc., four overhead cranes, all with 26 feet of working height and 10 tons lifting capacity, provide ample flexibility to produce a superior galvanized product.
05.
Quench
Once galvanized, the material may be quenched in water to reduce its temperature and to allow safe handling. The material may also be immersed in a chromate solution effective in reducing the formation of zinc oxide, or what is commonly referred to as white rust or wet storage stain.
06.
Inspection
Once galvanized, all material is inspected using both visual inspection and electromagnetic induction testing to ensure conformance with the specifications CSA G164-1981M and ASTM A123.
SPECIFICATIONS
| Specifications | Description |
|---|---|
| CSA G164-1981M | Hot Dip Galvanizing of Irregularly Shaped Articles. |
| ASTM A123 | Zinc (Hot Galvanized) Coatings on Products Fabricated from Rolled, Pressed, and Forged Steel Shapes, Plates, Bars and Strip |
| ASTM A143 | Safeguarding Against Embrittlement of Hot Dip Galvanized Structural Steel Products and Procedure for Detecting Embrittlement |
| ASTM A153 | Zinc Coating (Hot Dip) on Iron and Steel Hardware |
| ASTM A767 | Zinc Coated (Galvanized) bars for concrete reinforcement |
| ASTM A780 | Repair of Damaged Hot Dip Galvanizing Coatings |
GALVANIZING VS. PAINT
Hot-dip galvanized steel is coated with zinc, which is metallurgically bonded to the steel. Removal of the zinc coating can only be accomplished through substantial force. Unlike paint, zinc will not allow the environment to “creep” under the coating, causing premature coating failure. Zinc bonds perpendicular to the steel surface, causing an even layer throughout – even over sharp corners. In contrast, paint tends to recede from sharper areas, effectively reducing the coating value in these regions.
