Industrial Hot Dip Galvanizing and Corrosion Protection: A Comprehensive Technical Guide
A significant portion of the steel produced worldwide is rendered unusable or destroyed every year due to corrosion (rusting). Steel, which is the cornerstone of modern infrastructure, from power transmission lines to highway barriers, from massive industrial plants to city furniture, tends to react with oxygen and moisture and return to its old state, namely iron oxide. This inevitable law of nature is reflected in the global economy as billions of dollars in maintenance and repair costs.
At İES Galvaniz, we produce the strongest shield against this costly process: Hot Dip Galvanized (SDG).
In our integrated plant in the Osmaniye Organized Industrial Zone, with an annual capacity of 120,000 tonswe don’t just coat steel; we turn it into a maintenance-free building material for over 50 years. In this guide, we will examine all the details of the hot-dip galvanizing process, from the science of corrosion to our production technologies, from the advantages of our 14-meter-long galvanizing boiler to the technical design criteria.
1. The Science of Corrosion and the Protection Mechanism of Galvanizing
Without understanding corrosion, it is difficult to understand the value of the solution. Corrosion is the deterioration of a metal as a result of a chemical or electrochemical reaction with its environment. For steel, this process begins when oxygen and moisture in the air come into contact with the surface. But Hot Dip Galvanizing stops this process with three different lines of defense.
A. Barrier Protection
The hot-dip galvanizing process creates a thick, non-porous layer of zinc on the surface of the steel that is held in place by a metallurgical bond. This layer physically prevents corrosive electrolytes (rainwater, moisture, industrial gases) from reaching the underlying steel. Unlike paint systems, this layer is integral to the steel and will not peel off the surface.
B. Cathodic Protection
Herein lies the greatest miracle of galvanizing. Zinc is a more “active” (negative potential) metal in the electrochemical series than iron. Even if a deep scratch occurs on the coating during transportation or assembly and the steel is exposed, corrosion cannot attack the steel. The surrounding zinc oxidizes by sacrificing itself (as a sacrificial anode) and continues to protect the steel. This property is not present in paints or epoxy coatings; when paint is scratched, rust starts at the scratch and works its way under the paint.
C. Zinc Patina
When the galvanized surface is exposed to the atmosphere, a layer of zinc oxide, zinc hydroxide and finally zinc carbonate (patina) forms over time. This matte gray layer is insoluble in water and extremely stable, slowing down the melting rate of the coating and extending its protection life.
2. IES Galvanizing Process Flow: The Chemistry of the Perfect Coating
A quality galvanized coating starts with surface preparation long before the moment of dipping. The process applied in IES Galvanizing facilities consists of the following steps in full compliance with TS EN ISO 1461 standards
Step 1: Surface Cleaning and Preparation (Key to Success)
A dirty surface does not react with zinc. Therefore, the steel passes through the following baths in order:
- Degreasing: Cutting fluids, grease and oils formed during manufacturing are cleaned in alkaline baths.
- Acidizing (Pickling): Rust, scale (oxide layer) and weld stains on the steel surface are completely removed with hydrochloric acid solution. The result is a “virgin steel” surface.
- Rinsing: Acid residues are removed with water.
- Fluxing:The material is immersed in Zinc-Ammonium Chloride solution to prevent re-oxidation of the steel and to initiate the reaction with zinc.
Step 2: Galvanizing (Hot Dipping)
The dried material is immersed in a bath of molten pure zinc (99.995% Zn) at 450°C (±5°C). At this temperature a diffusion reaction takes place between iron and zinc. Alloy layers (Eta, Zeta, Delta, Gamma) of different hardness and composition are formed on the steel surface from the outside to the inside. These layers ensure that the coating does not “stick” to the steel, but rather “integrates” with it.
Step 3: Cooling and Control
The material removed from the pool is cooled in a controlled manner with air or water. Our quality control unit makes the product ready for shipment by performing micron thickness, surface appearance and adhesion tests.
3. Critical Advantage: 14 Meters Galvanized Boiler and Single Dip Technology
One of the most important factors determining quality in the galvanizing sector is “Boiler Size”. IES Galvaniz is one of the leading facilities in Turkey and the region with its 14 meter long galvanizing boiler.
Single Immersion vs. Double Immersion: Why It Matters?
Many facilities have 7-8 meter pools. When a 10-12 meter lighting pole or energy console arrives, these companies coat the material by first dipping it from one end and then from the other end (Double Dipping). However, this method carries technical risks:
- Scar and Aesthetic Problems:A thick scar forms at the midpoint where the two dips intersect.
- Shattering Risk:The risk of distortion due to thermal shock increases as the steel is exposed to 450°C heat at different times.
- Coating Imbalance:Coating thickness at midpoint may be non-standard.
IES Galvanizing Advantage: We coat parts up to 13-14 meters in SINGLE TIME (Single Dip). This results in a perfect surface that is homogeneous, smooth, seamless, without seam marks and with minimized thermal stress.
Giant Capacity for Big Projects
Our annual galvanizing capacity of 120,000 tonsallows us to offer a “deadline guarantee” especially in projects such as airports, highways, solar power plants where thousands of tons of steel need to be processed in a short time.
4. Technical and Economic Advantages of Galvanized Coating
Cost in engineering decisions is not just “initial purchase”; “Total Life Cycle Cost” (LCC) is essential.
- 50+ Years Maintenance Free Life:In rural and light industrial environments, galvanized coating can last between 50 and 80 years without maintenance. Considering the cost of sandblasting and repainting a painted pole every 10-15 years, galvanizing is the most economical solution.
- Full Protection Inside and Out:When painting hollow materials such as pipe poles and box profiles, the spray gun cannot reach the interior. However, with the dipping method, the liquid zinc penetrates into the material and covers the inside surfaces as perfectly as the outside. This prevents the poles from rotting from the inside.
- Impact and Friction Resistance: Iron-Zinc alloy layers are harder than the base metal (steel). This improves the material’s resistance to impact during transportation and assembly in the construction site environment.
5. Design Guide for Engineers and Manufacturers
There are some design rules to be considered during the manufacturing phase for a flawless galvanizing quality. IES Galvaniz engineering team provides technical consultancy to its customers in this process.
A. Ventilation and Drainage Holes
Hot dip galvanizing is a liquid process. The air in the material entering the zinc bath must come out and the excess zinc must flow out of the pool.
- Rule:“If the air doesn’t come out, the zinc doesn’t go in.”
- If holes of appropriate diameter are not drilled in closed volumes (pipes, profiles), the air trapped inside can expand at 450°C and cause an explosion. This creates a safety risk and deforms the material.
B. Steel Chemistry (Silicon and Phosphorus Ratio)
The chemical composition of the steel determines the thickness and brightness of the coating. Silicon (Si) and Phosphorus (P) ratios are particularly critical (Sandelin Curve).
- Sandelin Range:When the Si content is between 0.03% and 0.12%, the reaction is very fast and the coating can be thick, dull gray and brittle.
- İES Galvaniz warns its customers about the right choice of steel and ensures that the coating thickness meets aesthetics and standards.
C. Welding and Surface Defects
Welding slags (slag), paint, varnish or label residues on the material are not removed in the acid bath. These areas will not hold galvanization (black stain). It is important for fabricators to perform mechanical cleaning before galvanizing or use silicone-free welding sprays.
6. TS EN ISO 1461 Standards and Quality Assurance
İES Galvaniz applies the internationally recognized standard TS EN ISO 1461 (Hot dip galvanized coatings on materials made of iron and steel – Specifications and test methods) in all production processes. We can also produce according to the American standard ASTM A123.
Standard Coating Thicknesses (ISO 1461 Example):
| Steel Thickness (mm) | Minimum Average Coating Thickness (µm) | Minimum Average Coating Mass (g/m²) |
| > 6 mm | 85 µm | 610 g/m² |
| > 3 mm – ≤ 6 mm | 70 µm | 505 g/m² |
| ≥ 1.5 mm – ≤ 3 mm | 55 µm | 395 g/m² |
| < 1.5 mm | 45 µm | 325 g/m² |
Magnetic thickness measurements and adhesion tests performed in our laboratory certify each batch of products and report to the customer.
7. Hot Dip Galvanizing vs. Other Coating Methods
| Feature | Hot Dip Galvanized | Industrial Paint / Epoxy |
| Link Structure | Metallurgical (Alloy) | Physical (Surface adhesion) |
| Scratch Resistance | High (Self-repairs) | Low (Pass walks) |
| Inner Surface Protection | 100% Full Protection | Not possible / Very difficult |
| Need for Care | None (50+ Years) | Periodic (10-15 Years) |
| Application Period | Fast (Several hours) | Slow (waiting between floors) |
Duplex Systems: In projects with extra long life or aesthetic color demands (such as urban lighting poles), paint application (Duplex System) can be applied on galvanized. IES Galvaniz can also perform surface roughening processes suitable for paint.
8. Sectoral Applications: Where is Galvanized Used?
İES Galvaniz’s solutions can be found in all areas of life:
- Energy:High voltage lines, substations, distribution poles.
- Transportation: Guardrails, bridge railings, signaling poles, railway catenary systems.
- Solar Energy (SPP):Panel carrier constructions (Corrosion resistance is critical for return on investment).
- Construction and Building:Steel construction buildings, facade cladding, reinforcement in concrete.
- Agriculture and Livestock: Greenhouse constructions, feeders and paddocks.
9. Sustainability and Environment
Galvanizing is an environmentally friendly protection method.
- Resource Efficiency:Extends the life of steel, conserving the world’s iron ore and energy resources.
- Recyclability:Zinc and steel are 100% recyclable materials. When a galvanized structure reaches the end of its life, it can be melted down and reused.
- Non-toxic Process: IES Galvaniz, in accordance with its environmental policies, uses closed circuit acid systems and filtration units to produce without harming the nature.
10. Frequently Asked Questions (FAQ)
- Can galvanized material be welded?
Yes, it can be done, but the welding heat burns the zinc in that area. After welding, that area should be repaired with “cold galvanizing spray” or zinc maintenance paints. Ideally, galvanizing is done after the manufacturing is finished.
- What is White Rust?
If newly galvanized materials are stacked on top of each other in a stuffy and humid environment, a white dusty layer may form on the surface. This is zinc oxide. It is usually an aesthetic problem and does not seriously affect coating life. To prevent this, materials should be stored in a ventilated condition.
- Can the galvanized surface be painted?
Yes. However, the fresh galvanized surface is slippery. In order for the paint to adhere, the surface should be slightly roughened (sweep blasting) or a special primer (wash primer) should be used.
- What are the deadlines of IES Galvaniz?
With our capacity of 120.000 tons and 24/7 shift system, we offer the fastest delivery times in the industry. You can contact our sales team for planning according to project tonnage.
Don’t Rust the Future
Steel is strong, but it becomes immortal with galvanization. İES Galvaniz is ready to add value to your projects with its giant 14-meter galvanizing boiler, superior technology and expert staff. Whether it is a single pole or a highway project of thousands of tons; we protect your steel with our uncompromising approach to quality.
Don’t leave corrosion risk to chance. Meet IES Galvaniz, the galvanizing base of Turkey and the Middle East.