Galvanizing Process

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1.Quality Assurance

  • 1.Falcon Zinc Metal Industries provides all clients with a comprehensive Quality Control and Quality Assurance package inclusive of documentation deemed necessary such as Inspection Reports and Test Plans.
  • 2.Client’s comments can be incorporated based on their specific requirements once reviewed by the management of Falcon Zinc Metal Industries.
  • a. Reference: British Standard BS EN ISO 1461:2009 ASTM A 123/A 123M-02 ASTM A153/A 153M-01a

2.Receiving Material

  • 1.Items received for galvanizing are thoroughly inspected by our Receiving Foremen and Supervisors, and cross referenced against client specification and delivery documentation for:
    • a.Accurate quantities.
    • b.Elements are checked for the condition upon loading and any damage.
    • c.Elements dimensions are measured and their shapes analyzed to verify if they are suitable for our bath.
    • d.Venting arrangements are thoroughly checked to ensure compliance and suitability.
    • e.As there is considerable amount of heat involved in the process of galvanization, the susceptibility to distortion for the element needs to be evaluated.
  • 2. Once these checks are conducted, the delivery documentations are signed and the inspection concluded. Any discrepancy is forwarded to the client for their remedy.
  • 3. A Job Card is then issued detailing the client’s specific requirement and submitted to the management of Falcon Zinc Metal Industries for their review. The purpose of this is to ensure that the Galvanizing Foremen and Supervisors have all the required information insofar the required coating thickness; delivery schedule and any finishing related requirements are concerned.
  • 4.All elements are henceforth identified using the numbers stated on the Job Card.

3.Blasting & Degreasing

  • 1.Our foremen and supervisors determine the appropriate blasting method. Depending upon the size, type, shape and condition of the article, automatic, manual or a combination is utilized. For Automatic Shot Blasting, steel shot of size S330 or a mixture of S280 & S330 is used, whilst for Manual Blasting Garnet of size 30-60 is generally used.
  • 2.If the steel surface contains heavy oil or grease, it is immersed in the acid degreasing tank. After acid degreasing is carried out, the element is rinsed carefully with water. Degreasing works to remove organic contaminants such as dirt, paint markings, grease, and oil from the metal surface. The degreasing process is carefully monitored to the strictest of standard. Independent Third Party Inspectors are appointed to analyze samples to ensure this process is managed effectively.
  • 3.Epoxies, vinyls, asphalt, or welding slag, which cannot be removed by degreasing, must be removed before galvanizing by grit-blasting, sand-blasting or other mechanical means. Elements are blasted to ensure that the surface is entirely free of rust and other visible contaminants.
  • 4.Blasted to a surface finish of SA 2 ½. Surface profiles are maintained between 40-80 microns as a matter of common practice. Blasted articles are inspected by our Foremen and Supervisors though the utilization of a special Surface Finish Chart.
  • 5.The results are then recorded in a carefully managed Production Log.
  • 6.Sometimes elements are inspected after blasting to see if any contaminants can be removed using the pickling process. If this fails them, they are rejected and returned for additional blasting which is carefully recorded in the Production Log.

4.Preparation

  • 1.Our Foremen and Supervisors decide on method of element suspension into the bath. This is done either through tying or by hanging them onto our standard Jigs and the decision is based on the following criteria:
    • a)Shape, size & weight of the article
    • b)Position of venting & drainage holes (if applicable).
    • c)Availability of wiring points.
  • 2.Vent holes are drilled with consent from the customer on an as needed basis.
  • 3.The elements are along the frame in a manner such that no permanent contact takes place.
  • 4.The frames are then attached to the Gantry Cranes and the articles are once again checked for distribution uniformity and the accuracy of placement of venting holes and drainage.
  • 5.The Production Log is accordingly updated based on the above procedure

5.Pickling

  • 1. A dilute solution of heated sulfuric acid or ambient hydrochloric acid removes mill scale and iron oxides (rust) from the steel surface.
  • 2.Blasted/Degreased elements are immersed for around two minutes in the pickling solution.
  • 3.Comprising of Commercial Grade HCL Acid (32%) diluted to approximately 15%.
  • 4.All non-blasted elements shall be blasted after the pickling process is concluded. Non blasted/Nondegreased elements are dipped for a period not less than 5 minutes or until clean i.e. uniformly colored (re-dipping is used when necessary).
    Material Inspection Criteria Result
    Mild Steel Uniform bluish/grey color with no brown stain. Pass
    Cast Iron Uniformly clean appearance Pass
  • 5. Our Foremen and Supervisors visually inspect elements for cleanliness after pickling as follows:
  • 6. If rejected, this process is repeated as required.
  • 7. The results of the post pickling inspection are recorded in the Production Log.
  • 8. The acidity and refreshing of the HCL solution is maintained by adding a solution of HCL and water as required and until the appropriate concentration is attained. Our own Quality Control team monitors this process very carefully to sure efficiency in this process.
  • 9. Samples are regularly sent to our approved Third Party Laboratory to ensure compliance to approved method statements insofar the strength of the acid is concerned.

6.Rinsing

  • 1.Pickled elements are dipped into the rinsing baths and suspended over a period of time whereby all water is drained from the elements.
  • 2.Our Quality Control team monitors this process carefully to ensure compliance with the approved method statements. Again, samples are sent to a Third Party Laboratory on a regular basis to monitor pH levels and effective calibration.

7.Fluxing

  • 1.The final surface preparation step in the galvanizing process, a zinc ammonium chloride solution, serves two purposes. It removes any remaining oxides and deposits a protective layer on the steel to prevent any further oxides from forming on the surface prior to immersion in the molten zinc.
    • Available facility for this process
    • N° of tanks:1
    • Size of the tank: Length 14.5mt x Depth 2.7mt x Width 1.6 mt
    • Total content of 1 tank: 62 cu.m Product
    • Solution in the tank : 585 Kg per m3 of the solution
    • Product: salt of ZnCl2 2NH4Cl (weight = 56% ZnCl2, 44% NH4Cl).
    • Solution in the tank : 585 Kg per m3 of the solution
    • Solution temperature: 45°C
  • 2.Rinsed elements are immersed in the flux bath, which comprises of Zinc Ammonium Chloride and Water for at least two minutes, raised and suspended above the bath until there is no more run off. (Pure metallic contact with each other).
  • 3.The concentration of Zinc Ammonium Chloride is carefully measured in order to determine how much flux or water is needed to maintain the required concentration.
  • 4.The effectiveness of the fluxing process is monitored by our Quality Control team to ensure compliance with the approved Method Statements. Again, samples are sent to a Third Party Laboratory on a regular basis and recorded for effective calibration.

8.Zinc Bath Drip

  • 1.The bath temperature will be around 449⁰ C. At this temperature, zinc will react with icon in the steel and forms a coating consisting of layers of Zinc and iron alloy on the steel surface. The purity of the Zinc bath stands at 98.5 percent with 99.99 percent Zinc ingots utilized. The material shall be galvanized at610gm per square meter as per BS EN 1461 & applicable ADMA standards.
    Our Kettle is fully enclosed with specially designed enclosure consisting of two parts, fixed part above the Kettle directly with access gates from both ends. And a moving part attached to the specially designed overhead crane.
  • 2.Elements are suspended abovethe zinc bath to assist flux drying and preheating.
  • 3.The surface ofthe molten zinc is skimmed to remove oxides and flux residues (dross) prior to dipping the articles.
  • 4.Suspended elements are slowly dipped at an inclined position until fully immersed.
  • 5.Depending onthe type and thickness of the section, the element remains immersed until violent reactions have ceased.
  • 6.The elements are swung and agitated to assist wetting.
  • 7.The zinc surface is skimmed,the elements are slowly withdrawn inclined to allow free drainage of excess zinc and avoid lumps. Unsolidified excess zinc is removed by scrapers.
  • 8.Our dedicated Quality Control Team continually monitors the purity of Zinc to ensure the appropriate levels of purity are consistently achieved. Samples are regularly sent to a Third Party Laboratory for further verification.
  • 9.The results of the visual inspection of galvanizing surface are recorded in the Production Log.

9.Cooling

  • 1.The element’ssuitability for quenching is assessed by the Supervisor or Foreman.

    The facility available for this process is

    • Steel tank
    • Size of the tank: Length 14.5mt x Depth 2.7mt x Width 1.6 mt
    • Media: Cold water
  • 2.Elements that may suffer distortion during quenching are cooled naturally by lowering ontothe concrete floor (Welded sections, articles with low thickness & longer sections are prone to distortion when quenched in water).
  • 3.Elements that will not suffer distortion are quenched in water by gradually immersing into the quenching bath in amanner that will enable thesteamto escape safely.
  • 4.Cooled and quenched elements aremovedtothe cleaning inspection operation.
  • 5.The effectiveness of the quenching process is monitored in-house ona daily basis to maintain efficient process control. Samples from the quenching tank are monthly sentto an independent lab and results are recorded in the calibration record.

10.Cleaning & Final Inspection

  • 1.Grinders are used to ensure excess lumps are removed and a consistent final coat is achieved.
  • 2.Wiring markings are cleaned andtouched up with zinc rich paint.
  • 3.The elements are inspected to ensure freedom from gross Imperfections.Faults are reportedtothe Quality Inspector who investigates and determines whether to reject the article.
  • 4.Elements, which are rejected and reworked, are inspected.
  • 5.Coating thickness is measured with a calibrated Elcometer and recorded onthe Element Inspection Record. This final inspection record is treated asthe release note for dispatch.
  • 6.An adhesion check generally implies that the element can withstand normal handling. Normal handling doesnot include bending, curving and working. When required, adhesion is carried out with the help ofa pivoted hammer.
  • 7.Coating certificates are provided if requested.
    • a.Visual Inspection: 100%
    • b.Coating Thickness Checking: 100%
    • c.Coating Thickness Recording: In batches of 5 readings each