Season 9 Challenges

OPENED ON: 24 FEB 2020  |  CLOSING ON: 24 MAY 2020  |  REWARD: INR 3,00,000
Reward money is paid in exchange of legally acquiring the solution, implementing it to solve the problem and meeting the success criteria. Milestones for paying the reward money would depend upon the complexity of challenge and maturity of the proposed solution, which would be discussed with the solver as soon as the proposed solution is selected by us.

Short Description:

We are looking for low-cost handheld devices to accurately measure the zinc coating thickness of GI wires.

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Challenge Details

Galvanization or galvanizing is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method of galvanization is hot-dip galvanizing, in which the parts are submerged in a bath of molten hot zinc. We have a continuous hot-dip galvanization setup for producing galvanized iron (GI) wires. The molten zinc bath is maintained at 450oC, through which 40 galvanizing wire lines run parallelly. The steel wires pass through this molten zinc bath at line speeds of 40 to 130 m/min. The smaller diameter wires move at higher speeds and vice versa. Thus, the coating thickness is lower for thin wires and higher for thick wires owing to the varied residence time in the molten zinc bath. The wire diameters range from 1.4 - 5 mm and corresponding zinc coating range from 50 - 300 gsm.

Zinc is a major consumable for GI wire production. Often, it is observed that there is a variation of zinc coating across the length of wire. The actual coating thickness often becomes more than the desired coating thickness. This results in material loss due to increased zinc consumption as well as variation in final product quality delivered to the customer. 

Currently, we undertake offline zinc coating tests (volumetric zinc coating as per IS 6745) wherein we need to cut a test sample after production of approx. 1 MT wire. This is a reactive mode of determining the coating thickness and does not give continuous feedback to the operators. Any necessary corrective action is thus significantly delayed.  Hence, we are looking for a portable zinc coating measurement equipment which will help the operator to monitor zinc coating as and when required, without having the need to cut the test samples. This will enable frequent monitoring of the coating thickness, based on which corrective actions can be taken.

In case of concerns raised by customers regarding the coating, the provision of a portable thickness measuring device will eliminate the need of carrying back a cut sample from customer setup and testing at our laboratories by a volumetric testing method. Also, cutting a test sample is often not possible since wires are continuously formed into wire products and cutting a test sample in between (from the regions of concern) may lead to wastage of the entire bundle at the customer end. Thus, the need for a non-destructive test at the customer end is important and can be carried out if such a portable wire coating thickness measuring device is available. In this way, we will be able to reduce material losses resulting from excess zinc coated on the wires. This will also enable better coating consistency provided to the customer.

Options Tried:

  • Portable zinc coating probes are available for flat Galvanized sheet products. Similar probes are not applicable for wires because the wires are round in shape and a very small surface area is available for measurement.
  • There are few offline testing devices, which are highly expensive and not portable (handheld). Thus, during testing, samples must be cut and brought to the machine.
  • We have installed eddy current based zinc coating sensors at the heavy coating lines (300 gsm). However, these sensors are not suitable for low coating lines since the detection of coating thickness is a problem. Also, the existing sensors have limitations of accuracy (± 15 gsm) because of wire vibrations resulting from wire running speeds up to 130 mpm.


  • The device needs to be portable, handy, and easy to operate, with a preference for clamp-on types.
  • The device should have accuracy of ± 1 gsm  to achieve consistent coating after getting accurate feedback from measuring equipment.
  • The device should give repeatable results.
  • The device should be long-lasting and sturdy since it will be handled multiple times.


  • The curved surface of the wires poses difficulty in evaluating the coating thickness.
  • There are 40 galvanizing wire lines running in parallel.
  • The diameters of the wires range from 1.4 mm to 5 mm.
  • The coating thickness of the wires varies from 50 gsm - 300 gsm, i.e. 7 microns to 50 microns.

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