An Overview of Inspection of Hot Dip Galvanized Products

Durability is a key feature of hot dip galvanized products, ensuring maintenance-free performance for decades. Inspection of the finished product is essential to ascertain whether the coating is in compliance with applicable specifications. One of the most important aspects of inspection of hot dip galvanized products is to check the component’s fabrication prior to galvanizing. Once the galvanization process is complete, its inspection is necessary to measure the coating thickness and identify defects.  

Though it is the simplest of inspection techniques, visual inspection is considered to be an effective means to assess the quality of a galvanized coating. An important characteristic feature of galvanization is that continuous coatings with satisfactory appearance are generally sound and adherent. Therefore, it is essential that inspectors inspect any finished product for coating thickness as well as appearance.  

Inspection before Dispatching to the Galvanizer 

Fabricated castings, assemblies, and other components must be inspected before they are dispatched to the galvanizer. This is done to ensure that all the components are suitable for galvanizing. Timely inspection helps avoid delays and expensive rectifications at the galvanization plant. 

Size and shape: It is important to check whether all items to be sent for galvanizing are sized and dimensioned suitably for the facilities available at the galvanizing plant.  Sending items that the galvanizer can’t process can be a costly mistake. 

Structural steel: It is also important to ensure suitability of the steel used for galvanizing. Please check if the shearing, punching, and bending have been carried out. 

Satisfactory galvanizing: Observe the points mentioned below to ensure optimum galvanized product quality as well as minimum delays and additional expenses.  

  • Find out if the ‘fit for purpose’ requirements have been considered in the fabrication and whether the galvanizer is aware of these requirements. 
  • To ensure safety and satisfactory galvanizing, check that all hollow structures and closed vessels are vented. 
  • All structural sections and welded frames should also be vented to ensure that there are no air pockets and free drainage is possible across all surfaces.
  • Similarly, all overlapping surfaces must be vented sufficiently. 
  • Don’t forget to remove welding slag and spatter 
  • Your assemblies may get distorted while encountering high temperature of the molten zinc bath. Check whether all such assemblies have been braced appropriately. 
  • Check whether appropriate marking, both permanent and temporary, have been provided. 


As mentioned earlier, the ideal galvanized coatings should be continuous, without any inclusions and gross surface imperfections. Please remember that the corrosion resistance of the coating has nothing to do with differences in colour and lustre of galvanized coatings.  Also, the coating performance doesn’t get affected by the presence or absence of spangle. Compared to bright or spangled coatings, matt grey galvanized coatings often provide equal or better life. 

Coating Thickness Test 

Magnetic gauges are highly preferred for measurement of galvanized coating thickness because they are fast, reliable, and non-destructive.  Coating thickness readings are provided by magnetic gauges over very small areas. This is why it is important to take several readings and calculate the average.

Magnetic gauges make it effortless to measure actual thickness as well as uniformity of the thickness. However, it is not possible to obtain accurate reading near edges. Readings are also affected by steel thickness, surface area, and surface curvature. Therefore, allowances must be made to account for these factors.   

If you have any other questions about inspecting hot dip galvanized products, please contact us at Coating Management Solutions. We are one of Australia’s most preferred destinations for coatings identification and failure analysis.