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 in mass production considering the following benefits

Ø  Low cost

Ø  High productivity

Ø  Long Life of coating

Ø  Coating resistance quality

Ø  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  Third-Party Inspection of Galvanized products, can prepare the inspection Checklist considering the followings (at least) – To deliver a sound inspection report on the 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 inspectors who are into third-party Inspection activities. To develop a Sound understanding and get prepared to deliver third-party Inspection services and make the supplier and buyer happy to utilize the professional services of the Third-Party Inspection Agency 

-          Raw material required for galvanizing process

-          Equipment used in Galvanizing process

-          Galvanizing process

-          What are the types of inspection carried out on the Galvanized products?

-          inspection references specifications for Galvanized products

-          Benefits of Hot Dip Galvanizing

-          Types of Defects in Galvanize process

-          Equipment used for inspection of Galvanized products.

 

 

The raw material required for galvanizing process & its compliances

Ø  Zinc ingots -  Ref min 98.50% purity as per IS 209: 1992

Ø  Sulphuric Acid Solution – Ref IS 2629 Concentration

Ø  Hydrochloric Acid Solution – Ref IS 2629 Concentration

Ø  Flux -  Ref IS 2629 Concentration

Ø  Furnace Oil as per requirements.

 

Equipment used in Galvanizing process

Ø  7- Processing Tank

Ø  Zinc Bath

Ø  Over Head Crane

Ø  Bins

Ø  Centrifuging Machine

Ø  Blower

Ø  Furnace

 

Galvanizing process

Ø  Degreasing

Ø  Rinsing

Ø  Picking

Ø  Rinsing

Ø  Fluxing

Ø  Drying

Ø  Zinc dip

Ø  Cooling & inspection.

 

 

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

 

Ø  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:

a)      5 mm thick and over

b)     Under 5 mm, but not less 2 mm

c)      Under 2 mm, but not less than

1.2 mm

 

610

460

340

3

Threaded work other than tubes

and tube fittings:

a)      10 mm dia and

b)     Under 10 mm dia

 

 

300

270

 

Ø  Pivoted Hammer Test for Zinc Coated Fabricated Products - 5mm difference 3-5 impression

Ø  Knife Test for Zinc; Coated Hardware and Assembled Steel Products - No Peal off

Ø  Bend and Wrapping Tests for Zinc, Coated Steel, and Wire - 2T

Ø  Freedom from Defects - flux, ash bare patches, black, spots, pimples, lumpiness, run, rust stains, bulky white deposits, and blisters (Visual)

Ø  Post Treatment - chromating or phosphating

Ø  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

26-100

5

0

101-150

8

1

151-500

13

1

501-1000

20

2

1001-10000

32

3

100001 and above

50

5

 

 

What are inspection references specification for Galvanized products?

Ø  IS 2629 (1985) – Recommended practice for Hot Dip Galvanizing for iron & Steel (light Metals & Their Alloys)

Ø  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 the Galvanize process

Ø  Bare patches

Ø  Blasting Damage

Ø  Chair & Wore Marks

Ø  Black Ash

Ø  Cllagged holes & Threads

Ø  Distoration & Wrapages

Ø   Drainage Spikes

Ø  Dross Mark

Ø  Flakings

Ø  Flux markings

Ø  Oxide lines

Ø  Rough Surface/ Finishing.

Ø  Blisters

Ø  Pimples

Ø  Bulky white deposits

 

Equipment used for inspection of Galvanized products.

Ø  Elco Meter/ DFT Meter

Ø  Pivot Hammer

Ø  Knife

Ø  Hand press for bend test

Ø  Scratching tool

Ø  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 product inspection including the Inspection of Hot Dip Galvanized products. Any organization looking for an Inspection of Hot Dip Galvanized products may contact us.

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