Zhejiang Guanyu Stainless Steel Tube Co., Ltd  
  Directory | Useful Tool | Sitemap | Contact US | Home

         

Surface

HDG Hot Dip Galvanized Coating Thickness






The American Society of Testing and Materials International (ASTM), the Canadian Specification Association (CSA) and the American Association of State Highway and Transportation Officials (AASHTO) specifications establish minimum standard for thickness of galvanized coatings on various categories of items. These minimum standard are routinely exceeded by galvanizers due to the nature of the galvanizing process.

Factors influencing the thickness and appearance of the galvanized coating include chemical composition of the steel, steel surface condition, cold-working of steel prior to galvanizing, bath temperature, bath immersion time, bath withdrawal rate, and steel cooling rate.

The chemical composition of the steel being galvanized is very important. The amount of silicon and phosphorus in the steel strongly influences the thickness and appearance of the galvanized coating. Silicon, phosphorous or combinations of the two elements can cause thick, brittle galvanized coatings. The coating thickness curve shown in the figure below relates the effect of silicon in the base steel to the thickness of the zinc coating. The carbon, sulfur and manganese content of the steel also may have a minor effect on the galvanized coating thickness.

The combination of elements mentioned above, known as “reactive steel” in the galvanizing industry, tends to accelerate the growth of zinc-iron alloy layers. This may result in a finished galvanized coating consisting entirely of zinc-iron alloy. Instead of a shiny appearance, the galvanized coating will have a dark gray, matte finish. This dark gray, matte coating will provide as much corrosion protection as a galvanized coating having a bright appearance.

Even though it is not a part of the controlled composition of the steel, silicon may be present in many steels commonly galvanized. This occurs primarily because silicon is used in the deoxidization process in steel making and is found in continuously cast steel. The phosphorus content should never be greater than 0.04% for steel that is intended for galvanizing. Phosphorus acts as a catalyst during galvanizing, resulting in rapid growth of the zinc-iron alloy layers. This growth is virtually uncontrollable during the galvanizing process.

As the galvanizing reaction is a diffusion process, higher zinc bath temperatures and longer immersion times generally will produce somewhat heavier alloy layers. Like all diffusion processes, the reaction proceeds rapidly at first and then slows as layers grow and become thicker. However, continued immersion beyond a certain time will have little effect on further coating growth. When galvanizing reactive steels, the diffusion process proceeds at a faster rate, producing thicker coatings.

The thickness of the outer pure zinc layer is largely dependent upon the rate of withdrawal from the zinc bath. A rapid rate of withdrawal causes an article to carry out more zinc and generally results in a thicker coating.

ASTM, CSA and AASHTO specifications and inspection standards for galvanizing recognize that variations occur in both coating thickness and compositions. Thickness specifications are stated in average terms. Further, coating thickness measurements must be taken at several points on each inspected article to comply with ASTM A 123/A 123M for structural steel and A 153/A 153M for hardware.

Coating Thickness 2

It is difficult to provide precise guidance in the area of steel selection without qualifying all of the grades of steel commercially available. The guidelines discussed below usually result in the selection of steels that provide good galvanized coatings.

  • Levels of carbon less than 0.25%, phosphorus less than 0.04%, or manganese less than 1.35% are beneficial
  • Silicon levels less than 0.04% or between 0.15% and 0.25% are desirable

Coating Thickness 1

Related References:
1. About Zinc
2. About Hot-Dip Galvanizing
3. HDG Hot-Dip Galvanizing Last Time
4. Cost of Galvanized Steel
5. Selection of Zinc Coatings
6. Zinc Coatings-Galvanized|Electrogalvanized|Galvanneal|Galfan
7. Physical Properties of HDG Hot-Dip Galvanized
8. HDG Hot-Dip Galvanized Abrasion Resistance Resistance to Mechanical Damage
9. Hot-Dip Galvanized Corrosion Protection and the Zinc Patina
10. HDG Hot-Dip Galvanized High Temperature Exposure
11. HDG Hot-Dip Galvanized Surface Reflectivity
12. HDG Hot Dip Galvanized Coating Structure
13. HDG Hot Dip Galvanized Bond Strength
14. HDG Hot Dip Galvanized Coating Uniformity
15. HDG Hot Dip Galvanized Coating Thickness
16. Powder Coating Hot Dipped Galvanized Steel
17. Painting Hot-Dippped Galvanized Steel
18. Painting Hot-Dipped Galvanized Steel Surface Preparation
19. Surface Coatings for Corrosion
20. Hot-Dip Galvanizing Surface Preparation
21. Hot-Dip Galvanizing Galvanizing
22. Hot-Dip Galvanizing Inspection
23. Characteristics of Zinc
24. Hot-Dip Galvanizing Performance in Atmosphere
25. Hot-Dip Galvanizing in Atmosphere Time to First Maintenance
26. Hot-Dip Galvanizing Performance in Soil
27. Soil Corrosion Data for Corrugated Steel Pipe
28. Hot-Dip Galvanizing Performance in Water
29. Cause of Zinc Corrosion
30. Corrosion of Zinc Coated Steel in Selected Natural Fresh Water
31. Corrosion of Zinc and Zinc Coated Steel in Sea Water
32. Corrosion of Zinc Coating in Industrial and Domestic Water
33. Concrete Corrosion of Hot Dip Galvanizing
34. Concrete corrosion resistance of hot dip galvanized reinforcing
35. Removal of Forms Concrete Corrosion
36. Zinc Reaction in Concrete Corrosion
37. Concrete Corrosion References
38. Hot-Dip Galvanizing Performance in Chemical Solutions
39.Hot-Dip Galvanizing Performance in Contact with Other Metals
40. Hot-Dip Galvanizing Performance in contact with Treated Wood
41. Hot-Dip Galvanizing Performance in contact with Food
42. Hot-Dip Galvanizing Performance in Extreme Temperature

TubingChina.com All Rights Reserved

Directory | Standard | Heat | Heat Exchanger | Temperature | Pressure | Corrosion | Hardness | Surface | Properties | Select Stainless Steel | Contact US

Useful Tools:

Stainless Steel Weight Calculator
Metals Weight Calculator
Nickel Alloy Weight Calculator
Copper Brass Alloy Weight Calculator
Copper Brass Alloy Sheet Plate Weight Calculator
Sheet Plate Weight Calculator
Hardness Conversion Calculator
Hardness Conversion Chart
Rockwell Brinell Vickers Shore Hardness Conversion Chart
Conversion Calculator
Length Weight Temperature Volume Pressure Calculater
Pipe Working Pressure Calculator
Pressure Conversion Converter
Round Bar Size Calculator
Gauge Sizes
Sheet Metal Gauge
Pipe Schedule
Nominal Pipe Size
ANSI Pipe Chart
Inch to mm Chart
Stainless Steel Pipe Sizes
Stainless Steel Tubing Sizes Chart
Stainless Steel L H Grade
Stainless Steel Density
Conversion of Stainless Steel
Nickel Alloy Grades Comparison Material Grade Chart Carbon Steel
Structural Steel Comparison Chart



Main Products:

BA Tube | AP Tube
Condenser Tubes Tubing
Stainless Steel Reheater Tube Superheater Tubes
Stainless Steel U bend Tube
Nickel Alloy U bend Tubes
Copper Alloy U Bend Tubes
Heat Exchanger Tube
Super Duplex Pipe
Nickel Alloy Tube
Brass Alloy Tubing
Copper Nickel Alloys Tubes
Stainless Steel Hollow Tube
Stainless Steel Oval Tubing
Stainless Steel Square Tubing
Stainless Steel Rectangular Tubing
Stainless Steel Capillary Tube
Duplex Stainless Steel Pipe
Seamless Stainless Steel Tubing
Corrugated Stainless Steel Tubing
Stainless Steel Twisted Tube
Polishing Stainless Steel Tubing
Stainless Steel Aircraft Tube
Stainless Steel Hydraulic Tubing
Stainless Steel Instrumentation Tubing
Stainless Steel Angle Iron Bar
Stainless Steel Mechanical Tube
Bright Annealing Stainless Tube
Heat resistant Stainless Steel
Stainless Steel Welded Pipe
Extruded Serrated Finned Tubes Integral Finned Tubes / Extruded Aluminum Finned Tubes
Brass Alloys Copper Nickel Alloy Integral Low Finned Tubes
HFW High Frequency Welded Helical Spiral Serrated Finned Tubes
Corrosion Resistant Stainless Steel
Corrosion Resistance Stainless Steel

Stainless Steel Tubing Pipe

304 Stainless Steel Pipe
304L Stainless Steel Pipe
304H Stainless Steel Pipe
304/304L Stainless Steel Tubing
309S Stainless Steel Pipe
310S Stainless Steel Pipe
316L Stainless Steel Tubing
316Ti Stainless Steel Tube
317L Stainless Steel Pipe
321 321H Stainless Steel
347 347H Stainless Steel
904L N08094 Seamless Tubes
17-4 PH 630 UNS S17400 Stainless Steel
253MA S30815 Stainless Steel Tube
S31254 254 SMO Pipe
S31803 Stainless Steel
2205 Duplex Pipe Tubing
S32101 Stainless Steel
S32304 Stainless Steel
2507 Super Duplex Pipe
S32750 Super Duplex Pipe
S32760 Super Duplex Steel
1.4462 Stainless Steel Pipe
ASTM A213 | ASTM A269
ASTM A312 | ASTM A511
ASTM A789 | ASTM A790
ASTM B161 / ASME SB 161 | ASTM B111
EN 10216-5
ASTM A789 ASME SA 789 S31803 S32205 S32101 S32750 S32760 S32304 S31500 S31260 Seamless Tubes
EN 10216-5 1.4462 1.4362 1.4162 1.4410 1.4501 Seamless Tubes
Nickel Alloy Tubing:

UNS N08020 Alloy 20 Tubing
UNS N02200 Alloy 200 Tube
UNS N02201 Alloy 201 Pipe
UNS N04400 Monel 400 Tubing
N06600 Inconel 600 Tube
N06601 Inconel 601 Tubing
N06625 Inconel 625 Tubes
N08800 Incoloy 800 Tube
N08810 Incoloy 800H Tube
N08811 Incoloy 800HT Tubing
UNS N08825 Incoloy 825 Pipe
ASTM B622 N10276 C276 Tubing
ASTM B622 N06022 Hastelloy C-22 Alloy Tubes
C28000 Brass Seamless Tubes C44300 Brass Seamless Tubes
C68700 Brass Seamless Tubes
C70600 Copper Nickel Tubes
C71500 Copper Nickel Tubes
DIN 2391 Seamless Precision Steel Tubes
EN 10305-1 E215 E235 E355 Seamless Precision Steel Tube Tubing Tubes
DIN 2393 St28 St34.2 St37.2 St44.2 St52.3 Welded Precision Steel Tubes
EN 10305-2 E195 E235 E355 Welded Cold Drawn Precision Steel Tube