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Inspection of Hot Dip Galvanized products

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Inspection of Hot Dip Galvanized products

About Galvanizing

Galvanizing is the electrochemical process of providing Zinc coating to iron /Steel to prevent Corrosion and Rust.

This process of Zinc coating is widely used on Industrial and Domestic products on mass production considering the following benefits

  • Low cost
  • High productivity
  • Long Life of coating
  • Coating resistance quality
  • Uses for mass production with low cost and high reliability on surface protection.

 Hot-Dip Galvanizing

Hot-dip galvanizing is one of the most economical, maintenance-free corrosion protection systems available. Like any other manufacturing process, hot-dip galvanized steel requires an inspection of the finished product to ensure compliance with applicable specifications. The inspection process requires a clear understanding of specification requirements and compliance measurement techniques to make an accurate assessment.

Third-Party Inspection Agency – Involve in the inspection of Galvanized products, can prepare the inspection Checklist considering the following (at least) – To deliver the sound inspection report on inspection of Galvanized products.

The Following Points have been covered in the context of the Inspection of Galvanizing products. Which will help the Third-Party Inspection Agency in India or Inspector who are into third party Inspection activities? To develop the Sound understanding and get prepared to deliver the third-party Inspection services and make the supplier and buyer happy to utilize the professional services of Third-Party Inspection Agency  

  • The raw material required for the galvanizing process
  • Equipment used in the Galvanizing process
  • Galvanizing process
  • What are the types of inspection carried on the Galvanized products?
  • inspection references specification for Galvanized products
  • Benefits of Hot Dip Galvanizing
  • Types of Defects in Galvanize process
  • Equipment used for inspection of Galvanized products.

Raw material required for galvanizing process & its compliances

  • Zinc ingots –  Ref min 98.50% purity as per IS 209 : 1992
  • Sulphuric Acid Solution – Ref IS 2629 Concentration
  • Hydrochloric Acid Solution – Ref IS 2629 Concentration
  • Flux –  Ref IS 2629 Concentration
  • Furnace Oil as per requirements.

Equipment used in Galvanizing process

  • 7- Processing Tank
  • Zinc Bath
  • Over Head Crane
  • Bins
  • Centrifuging Machine
  • Blower
  • Furnace

Galvanizing process

  • Degreasing
  • Rinsing
  • Picking
  • Rinsing
  • Fluxing
  • Drying
  • Zinc dip
  • Cooling & inspection.

What are the types of inspection carried on the Galvanized products or Samples?

  • Mass of zinc coating
Sr NoProductMinimum Value or Average Mass of Coating (g/m2)
1Castings-grey iron, malleable iron610
2Fabricated steel articles: 5 mm thick and overUnder 5 mm, but not less 2 mmUnder 2 mm, but not less than 1.2 mm  610 460 340
3Threaded work other than tubes and tube fittings: 10 mm dia andUnder 10 mm dia    300 270
  • Pivoted Hammer Test for Zinc-Coated Fabricated Products – 5mm difference 3-5 impression
  • Knife Test for Zinc; Coated Hardware and Assembled Steel Products – No Peal off
  • Bend and Wrapping Tests for Zinc, Coated Steel and Wire – 2T
  • Freedom from Defects – flux, ash bare patches, black, spots, pimples, lumpiness, runs, rust stains, bulky white deposits and blisters (Visual)
  • Post Treatment – chromating or phosphating
  • Determination of Uniformity of Galvanizing Coating & Uniformity in Thickness (Sampling Plan)
No. of Units in the LotNo. of Units to be Selected in a SampleAcceptance No.
Up to 2530
26-10050
101-15081
151-500131
501-1000202
1001-10000323
100001 and above505

What are inspection references specification for Galvanized products?

  • IS 2629 (1985) – Recommended practice for Hot Dip Galvanizing for iron & Steel (light Metals & Their Alloys)
  • IS 4759 (1996) – Hot dip zinc coating on structural steel and other allied products (Light metals and their alloys)

Benefits of Hot Dip Galvanizing

Different Appearances The appearance of the hot-dip galvanized coating can vary from piece to piece, and even section to section of the same piece. Common appearances for hot-dip galvanized steel immediately after galvanizing include bright and shiny, spangled, matte gray, and/or a combination of these. There are a number of reasons for the non-uniform appearance; however, it is important to note appearance has no bearing on the corrosion protection of the piece. Furthermore, in time, after exposure to the environment, all galvanized coatings will take on a uniform, matte gray appearance

Types of Defects in Galvanize process

  • Bare patches
  • Blasting Damage
  • Chair & Wore Marks
  • Black Ash
  • Cllagged holes & Threads
  • Distortion & Wrapages
  •  Drainage Spikes
  • Dross Mark
  • Flakings
  • Flux markings
  • Oxide lines
  • Rough Surface/ Finishing.
  • Blisters
  • Pimples
  • Bulky white deposits

Equipments used for inspection of Galvanized products.

  • Elco Meter/ DFT Meter
  • Pivot Hammer
  • Knife
  • Hand press for bend test
  • Scratching tool
  • Chemical Lab for Mass of zinc coating test

We are a leading Third-Party Inspection agency in India providing a wide range of inspection services across India for engineering products inspection including Inspection of Hot Dip Galvanized products. Any organization looking for Inspection of Hot Dip Galvanized products may contact us.