Inspection of Hot Dip Galvanized products
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 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 – 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
- Centrifuging Machine
- Zinc dip
- Cooling & inspection.
What are the types of inspection carried on the Galvanized products or Samples?
- Mass of zinc coating
|Sr No||Product||Minimum Value or Average Mass of Coating (g/m2)|
|1||Castings-grey iron, malleable iron||610|
|2||Fabricated 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|
|3||Threaded 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 Lot||No. of Units to be Selected in a Sample||Acceptance No.|
|Up to 25||3||0|
|100001 and above||50||5|
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
- Flux markings
- Oxide lines
- Rough Surface/ Finishing.
- Bulky white deposits
Equipments used for inspection of Galvanized products.
- Elco Meter/ DFT Meter
- Pivot Hammer
- Hand press for bend test
- Scratching tool
- Chemical Lab for Mass of zinc coating test
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