Practical Guidelines for the Inspection and Repair of Hot Dip Galvanized Coatings

Practical Guidelines for the Inspection and Repair of Hot Dip Galvanized Coatings

Harshal S Khode

Associate Manager Technical/QA/QC/Civil/Structure

1 INTRODUCTION

Hot dip galvanizing is used as a very effective steel corrosion protection method, providing a long service-life. The corrosion protection is dependent on the coating thickness and environmental conditions (ASM Handbook, 1994). Zinc coated components are also used to give a good appearance to the constructions. In recent years the interest in hot dip galvanizing for decorative and constructional applications has increased. The difference in the field of use determines the requirements to the coating appearance.

Duller coating finish is desired in buildings, because shiny coatings with high reflectivity may cause problems with passing traffic. At the same time most customers prize the bright spangled look for decorative applications. As a result of customer demands the requirements to the coatings and especially to the appearance have increased. Coating appearance is affected by processing properties, steel chemistry, and substrate surface condition.

Traditionally, hot-dip galvanized steel is specified for its superior corrosion protection, especially in harsh environment. Though corrosion resistance is inherent any time galvanizing is utilized, more and more specifiers select hot-dip galvanized steel for other reasons, including lowest initial cost, durability, longevity, availability, versatility, aesthetics and sustainability.

This Case Study paper is prepared is based on Practical Experiences during my factory Inspection services for Hot-Dip Galvanizing products for Swicthyards, Solar Mounting structures, Transmission Line Towers, Pipe racks System in Oil and Gas Refineries, Petrochemical Complex, Light Gauge framing Structures (LGFS), Structural Components for PEB Buildings during 14 years of Experience for various industry like Oil and Gas Projects, Power Projects, and Renewal Energy sectors.

I have all Official ASTM Standards for available References along with American galvinizers Association Guides. These defects are very common during manufacturing and improper loading and unloading of Hot-Dip Galvanizing structural membrers during supplying the customers via closed shipping containers.

1. PURPOSE OF INSPECTION

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

   A key feature of hot-dip galvanized (HDG) product is durability, which yields decades of maintenance-free performance. For any environment, the time to first maintenance of HDG steel is directly proportional to the thickness of the zinc coating.

   Coating thickness is an important requirement in the specification and effectiveness of hot-dip galvanizing as a corrosion protection system. However, measuring coating thickness is only one of the many specification requirements in the inspection process. The inspection of hot-dip galvanized steel is simple and quick. The two properties of the hot-dip galvanized coating closely scrutinized are coating thickness and coating appearance. A variety of simple physical and laboratory tests may be performed to determine thickness, uniformity, adherence, and appearance.

   Products are galvanized according to long established, accepted, and approved standards of ASTM, the International Standards Organization (ISO), the Canadian Standards Association (CSA), and the American Association of State Highway and Transportation Officials (AASHTO). These standards cover everything from the minimum coating thicknesses required for various categories of galvanized items to the composition of the zinc metal used in the process.

   Testing methods and interpretation of results are covered in the publication, The Inspection of Products Hot-Dip Galvanized after Fabrication, published by the American GalvanizersAssociation(AGA).

2. MEASUREMENT OF COATINGS

   The specification give requirements concerning the amount of coating applied to the steel part during the hot-dip galvanizing process. The amount of coating can be specified by thickness or weight per surface areas. The specifications include tables providing specific requirements for thickness or weight per surface area based upon the steel part type and the measured steel thickness.

   The minimum coating thickness requirements specified by ASTM for different classes of works are summarized in following tables

   Table 1: Minimum Coating Thickness from ASTM A123/A123M

   MINIMUM AVERAGE COATING THICKNESS GRADE BY MATERIAL CATEGORY – ASTM A123/A123M (ROLLED, PRESSED AND FORGED SHAPES, CASTINGS, PLATES, BARS AND STRIPS)
   	(MM))
   	< 1/16 (<1.6)	1/16 to < 1/8 (1.6 to < 3.2)	1/8 to 3/16 (3.2 to 4.8)	> 3/16 to < 1/4 (> 4.8 to < 6.4)	> 1/4 (> 6.4)
   Structural Shapes	45	65	75	85	100
   	45	65	75	85	100
   	45	45	75	75	75
   	35	50	60	65	80
   					100

   • MATERIAL CATEGORY

   • ALL SPECIMENS TESTED (STEEL THICKNESS RANGE (MEASURED), IN

   • Strips and Bars

   • Pipe and Tubing

   • Wire

   • Reinforcing Bars

   Table 2: Chart for Coating thickness Grade

   Coating Thickness Grade
   Coating Grade		OZ/FT2	µm	G/M2
   35	1.4	0.8	35	245
   45	1.8	1	45	320
   55	2.2	1.3	55	390
   65	2.6	1.5	65	460
   75	3	1.7	75	530
   85	3.3	2	85	600
   100	3.9	2.3	100	705

   • Mils

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   Table 3: Minimum Coating Thickness from ASTM A153 / A153M

   MINIMUM AVERAGE COATING THICKNESS BY MATERIAL CLASS – ASTM A153/A153M (IRON AND STEEL HARDWARE)

   Class of Materials

   Minimum weight of zinc coating, OZ/FT2 (G/M2) of Surface

   Minimum Thickness Mils (Microns)

   Specimens

   Any Individual Specimens

   Class – A

   2.00 (610)

   1.8 (550)

   3.4 (86)

   3.1 (79)

   B – 1

   2.00 (610)

   1.8 (550)

   3.4 (86)

   3.1 (79)

   B – 2

   1.5 (458)

   1.25 (381)

   2.6 (56)

   2.1 (53)

   B – 3

   1.3 (397)

   1.1 (336)

   2.2 (56)

   1.9 (48)

   1.25 (381)

   1.00 (305)

   2.1 (53)

   1.7 (43)

   1.0 (305)

   0.85 (259)

   1.7 (43)

   1.4 (36)

   • Descriptions of Class of Materials

   • Average of Specimens Tested

   • Any Individual

   • Average of Specimens Tested

   • Castings, Malleable Iron and Steel

   • Class – B

   • Rolled, Pressed and forged articles (Except those which would be included under class C or D)

   • 3/16 in (476mm) and over in thickness and over 15 in (381mm) in length

   • Under 3/16 in (476mm) in thickness and over 15 in (381mm) in length

   • Any thick and 15 in (476mm) and under in length

   • Class – C

   • Fastners over 3/8 in (9.52mm) in diameter and similar articles, washers 3/16 in and 1/4 in (4.76 and 6.35 mm) in thickness

   • Class – D

   • Fastners over 3/8 in (9.52mm) in diameter and similar articles, washers 3/16 in and 1/4 in (4.76 and 6.35 mm) in thickness

   • Note: In this case of long pieces, such as anchor rods and similar articles over 5ft. (1.52mm) in length. The weight of coating shall be determine at each and the middle of the article. In no case shall individual measurement be below the minimum shown in the "Any Individual specimen" of column.

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   Table 4: Minimum Coating Thickness from ASTM A767 / A767M

   Minimum Coating Thickness by Class ASTM A767 / A767M (Reinforcing Bars)
   Coating Class		Mass of Zinc Coating Min. G/M2 of surface	Weight of Zinc Coating Min. OZ/FT2 of surafce
   Class 1		915	3
   		1070
   			3.5
   Class 2		610	2

   • Descriptions

   • Bar Designation size no. 10 (3)

   • Bar Designation size no. 13 (4) and Larger

   • Nil

   • Bar Designation size no. 13 (14) and Larger

   • Nil

   • Bar Designation size no. 10 (3) and Larger

3. Coating Thickness Measurement

Coating thickness refers to the thickness of the final Hot-dip galvanized coating. Two different methods are used to measure the coating thickness of hot-dip galvanized steel; a magnetic thickness gauge and optical microscopy. Utilizing a magnetic thickness gauge is a non-destructive, simply way to measure coating thickness. There are three different types of magnetic thickness gauges as below:

1. Pencil – style Gauge is pocket-size and employs a spring-loaded magnet encased in a pencil-like container (Figure no.1). Its accuracy depends on the skill of the inspectors, thus the measurement should be made multiple times.

   Figure 1: Pencil Style gauge

2. Banana Gauge, (Figure no.2) can measure coating thickness in any position, without recalibration or interference from gravity.

   Figure 2 : Banana Gauge

   The Electronic or Digital Thickness Gauge is the most accurate and easiest to use (Figure no.3). Electronic gagues can also store data and perform averaging calculations.

   Figure 3: Digital Thickness Gauge (Shoe or Gun type)

   The specification ASTM E376 Practice for measuring coating thickness by magnetic-Field or Eddy current (Electromagnetic) Examination Methods contains information on measuring coating thickness as accurately as possible.

   The other method to measure coating thickness, Optical microscopy, is a destructive technique that expose the edge of coating under an optical microscope (Figure no.4). The sample must be sectioned then mounted and polished to show the exposed edge of the hot-dip galvanized coating. The calibrated eyepiece of an optical microscope can then determine the thickness of the coating. Since this technique destroys the part being measured, it is only used as a reference method for resolving measurement disputes.

1. Coating Weight

   Coating weight refers to the mass of hot-dip galvanized coating applied to a product for a given surface area. Two different methods can be used to measure the coating weight of hot-dip galvanized steel. The first method uses a process called weight- galvanize-weigh, and is only appropriate for single specimen samples. Weigh-galvanize-weigh measures the weight of a steel part after it has been cleaned, and again after it has been galvanized. This technique only measures the zinc metal added to the steel and will underestimate the total coating weight by up to 10 percent.

   The second method is a destructive technique called weigh-strip-weigh, and again is only appropriate for single specimen samples. Weigh-strip-weigh measures the weight immediately after a galvanized part is cooled, and again after the coating has been stripped off the part using an acid solution. The weigh-strip-weigh renders the part unusable as the coating is removed. The weights must then be divided by the surface areas of the steel part to determine a value that can be compared to the specification requirements.

   Figure 4: Optical Microscpe

2. FINISH AND APPEARANCE:

   Several factors can affects the finish and appearance of hot-dip galvanized coatings. Some of these factors can be controlled by the galvanizers while others cannot. The inspection of finish and appearance is done with an unmagnified visual inspection, which is performed by fully observing all parts and pieces of a hot-dip galvanized product to ensure all specifications have been met. Visual inspection is done in order to observe surface conditions (both inside and cut) and to check all contact points, welds, junctions, and bend areas. The visual inspection should be completed at the galvanizing facility before the part is shipped.

   1. Different Appearance:

      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 combinatin 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.

3. ADDITIONAL INSPECTION TEST

1. Adherence Test

   Testing zinc coating adherence is achieved using a stout knife and smoothly running it along the surface of the steel without whittling and gouging, as detailed in the ASTM specification ASTM A123 / A123M and ASTM A153 / A153M.

2. Embrittlement Test

   When there is suspicion of potential embrittlement of a products, it may be necessary to test a small group of the products to measure the ductility according to the protocol in specification ASTM A143 / A143M practice for safeguarding against Embrittlement of Galvanized structural steel products and procedure for detecting Embrittlement.

3. Bending Test for Reinforcing Steel

   The hot-dip galvanized coating on a steel reinforcing bar must withstand bending without flaking or peeling when the bending test is performed in accordance with the procedure in ASTM A143 / A143M. Repairs is commonly bent cold prior to the hot-dip galvanizing process. When bending prior to galvanizing the fabricated bend diameter should be equal to or greater than the specified value in ASTM A767 / A767M.

4. Passivation Testing

   The specification to determine the presence of chromate on zinc surfaces is ASTM B201. This test involves placing drops of a lead acetate solution on the surface of the product, waiting 5 seconds, and then blotting it gently. If this solution creates a dark deposit or black stain, there is passivated zinc present. A clear result indicates the presence of a passivation coating.

1. SAMPLING METHODS

   A sampling protocol has been adopted by ASTM to ensure high quality products because the inspection of the coating thickness for every piece of materials galvanized in a project would not be practical. To properly evaluate hot-dip galvanized coatings, randomly chosen specimens are selected to represent the lot. The inspections quantities are determined by a lot sizes and are detailed in the ASTM specifications A123/A123M, A153/A153M and A767/A767M.

   For products whose surface area is equal to or less than 160 in2 (1032 cm2), The entire suface of the tested product constitutes a single specimen. Products containing multiple materials categories or steel thickness ranges and products with surface areas greater than 160 in2 (1032 cm2) are sampling is based on the total lot size (Number of pieces) and is defined in the ASTM specifications.

   For single specimen articles, specimens are randomly selected and a minimum of five widely dispersed measurement are taken over the surface area of each specimen to represent the average thickness. The average value of the five coating thickness measurement must be greater than or equal to one grade below the minimum average coating thickness for the material category. The average coating thickness of the lot (All specimens tested) must meet the minimum coating thickness for the material category.

   For multi-specimen products, the products surface area is subdivided. For Parts greater than 160 in2 (1032 cm2), three continuous local sections with equivalent surface areas constitutes a specimen. Each specimen (sub-section) must have five widely dispersed readings just as for single specimen articles. For fabrications with more than one material category or steel thickness, the fabrication will contain more than one specimen. Each specimens (sub-section) average thickness measurement values must be greayer than equal to one grade below the minimum average coating thickness for the material category, and the overall sample (Three susb-section averages) must meet the minimum average coating thickness for the material category.

2. FIELD INSPECTION

Inspection of hot-dip galvanized steel products does not end once they are accepted at the galvanizers facility or job site. Once erected, any good corrosion protection strategy includes periodic inspection and maintenance to ensure the protective coating is performing as expected. When inspecting hot-dip galvanized steel in the field, the inspector should be aware of potential ace;erated corrosion areas and aesthetic surface defects.

When inspecting a galvanized coating in the field, the number one concern is the number of years remaining before the coating will need to be touched-up or replaced. Fortunately, estimating the remaining time to first maintenance for hot-dip galvanized coatings in atmospheric exposures is relatively simple. For a ballpark estimation, use a magnetic thickness gauge to take a coating thickness measurement.

1. Visual Observations

In addition to talking coating thickness measurements, the galvanized coating can be visually inspected for signs of accelerated corrosion in specific areas. Thickness measurement should be taken in these areas to ensure adequate zinc coating remains or if touch up should be performed. Corrosion prone areas to inspect further include the following effects as:

1. Crevices

   When corrosive elements such as water penetrates crevices, the limited air flow can create differences in potential creating anodic and cathodic areas which canlead to corrosion. Some common areas include: overlapped areas, mated sections between fastners, and areas where the galvanized coating is butted up against another surface such a wood, concrete or asphalt. When possible, crevices should be avoided during the design process.

2. Dissimilar Metals in Contact

   When dissimilar metals are in contact, galvanic corronsion can occurs, zinc, which comprises the galvanized coating, is high on the galvanic series of metals; and therefore, will preferentially corrode to almost any other metal with which it is in contact. When Possible, preventing dissimilar metals from being in contact should be addressed during the design process. Electrically dissimilar metals from one another stops galvanic corrosion and can be accomplished by using plastic or rubber grommets between the dissimilar metals or by painting the cathode. When the surface area of the cathode is much larger than the anode, galvanic corrosion can quickly consume the anodic materials.

3. Areas Where Water pools

   Flat areas can collect water and other corrosive elements and can have higher corrosion rates than vertical surfaces. Visually observing galvanized steels flat areas and taking coating thickness measurements will ensure adequate corrosion protection remains. When possible, areas that collect water can be addressed by providing drain holes to prevent moisture from pooling on the surface for long period. If drain holes do exist, inspect the drain holes of the galvanized steel corrosion and touch up when necessary.

4. Previously Touched-Up Areas

   Areas of hot-dip galvanized steel previously touched-up either the initial coating or erection often corrode more quickly than the surrounding zinc coating and should be inspected visually and tested with a magnetic thickness gauge. These areas may be touched-up when necessary using the instructions listed in the touch-up and repairs section of this publication to extend the service life of the part.

   When inspecting galvanized steel in the field, there are a few common appearance issues you may observe. Most are surface or aesthetic conditions an dnot cause for concern;however; others may require attention and or maintenance. The most common appearance issues on galvanized steel after being in service for a number of years include.

   1. Brown Staining

      Often mistaken for corrosion, brown staining is a surface defect created when iron in the zinc-iron alloy layers oxidizes. As previously noted in this publication, sometimeshot-dip galvanized coatings from without a free zinc layer, leaving intermetallic layers on the surface. Also, as galvanized steel weathers, the eta layer will be consumed and can lead to this phenomenon. Brown staining forms when free iron in the intermetallic layers reacts with moisture in the environment and oxidizes, discoloring the surrounding zinc coating. To distinguish betwwen red rust and brown staining, simply test the area with a magnetic thickness gauge. If the gauge reading shows a coating thickness, it is brown staining is simply an aesthetic concern, touch-up is not necessary in the stained area, and it may be removed by brushing with a nylon bristle brush.

   2. Wet Storage Stains

      As addressed earlier in this specification, improper storage and tight stacking of galvanized products can lead to the development of wet storage stain or zinc oxide and hydroxide build-up on the surface (Figure below). If aglvanzied products are going to be stored before erection, it is important to properly vent the bundle to avoid the development of wet storage stain. For more information, see the below section for wet storage stain. Similar to the development of wet storage stain when storing materials, galvanized products in place that have moisture on the surface without the movement of free flowing air can develop oxides and hydroxides that look like wet storage stain. A common area for this to occur is on surfaces where snow is piled on the surface and left to melt or in areas where water pools for extended periods without drying. Wet storage stain occurs most often during the first month after galvanizing.

   3. Weeping Welds

      Weeping welds (See below figure) were discussed in this specification below, and tough they can seen immediately after galvanizing, often they occurs after the steel is in service. As reviewed earlier, weeping welds are mostly a cosmetic concern;however, corrosion can be accelerated in the area where the liquids and rust bleeding are leaking. To clean and seal weeping welds, you can wash away the oxides on the outer area and apply epoxy or caulk to the area to prevent water from penetrating the crevices in the future.

   4. Bare Spots

      The galvanized coating can be compromised during delivery, handling, erection, and while in use. Some cathodic protection is offered to bare areas of the steel by the surrounding galvanized coating, but these areas can still rust if the area is too wide or corrosive elements frequently attack the steel. Research has shown the galvanized coating offers cathodic protection to bare areas between 1mm to 5mm wide depending on the electrolyte that electrically connects the galvanized coating to the bare area. Bare areas should be touched-up in accordance with the procedures outlined in this specifications to ensure longevity of the surrounding coating.

      10 TOUCH UP AND REPAIRS METHODS

      The touch-up and repair of hot-dip galvanized steel coatings is important to maintain uniform barrier and cathodic protection as well as ensure longevity. Although the hot-dip galvanized coating is very resistant to damage, small voids or defects in the coating can occur during the galvanizing process or due to improper handling of the steel after galvanizing. Touch-up and repair of galvanized steel is simple whether newly galvanized or in service for years. The practice is the same, but there are more restrictions to the allowable repairs on a new product than one that has been in service.

      The main restriction in the specification for repairing newly galvanized materials is the size of the area which is outlined in the product galvanizing specifications (ASTM A123/A123M, A153/A153M and A767/A767M0. According to those specifications, the allowable surface area for repairs is no more than ½ of 1% of the accessible surface area to be coated on that article, or 36 in2 (2250 mm2) per ton of piece-weight, whichever is less. ASTM A780 practice for repairs of damaged and Uncoated areas of Hot-dip Galvanized coatings details how to repairs the damaged coating

      Another tenet of the specification for touch-up and repairs is the coating thickness of the repair area. Touch-up materials are required to meet a coating thickness of at least 2.0 mils (50.8 µm) for one application, and the final coating thickness of the repairs area is dictated by the material used to do the repair, outlined below.

      1. Zinc-Based Solders

         Soldering with zinc-based alloy is achieved by applying zinc alloy in either a stick or powder form. The area being repaired needs to be preheated to approximately 600 F (315 C). The acceptable material compositions of solders used for repair are included in the specification.

         Figure 5: Zinc-Based Solder Technique

         The final coating thickness for this repair shall meet the specification requirement for the material category for the steel part being repaired with a maximum thickness of 4 mils (100µm). The thickness shall be measured by any of the methods in A123/A123M that are non-destructive. Zinc-based solder products closely match the surrounding zinc and blend in well with the existing coating appearance.

      2. Zinc Rich Paints

         Zinc-rich paint is applied to a clean, dry steel surface by either a brush or spray. Zinc-rich paints must contain either between 65% to 69% metallic zinc by weight or greater than 92% metallic zinc by weight in dry film. Paints containing zinc dust are classified as organic or inorganic, depending on the binder they contain. Inorganic binders are particularly suitable for paints applied in touch up applications of undamaged hot-dip galvanized areas.

         Figure 6: Zinc Rich Paints

         The coating thickness for the paint must be 50% more than the surrounding coating thickness, but not greater than 4.0 mils (100

         µm), and measurements should be taken with either a magnetic, electromagnetic, or eddy current gauge to ensure compliance.

      3. Zinc Spray (Metallizing)

         Zinc spray, or metallizing, is done by melting zinc powder or zinc wire in a flame or electric arc and projecting the molten zinc droplets by air or gas onto the surface to be coated. The zinc used is normally 99.5% pure or better.

         Figure 7: Zinc Spray (Metallizing)

         The renovated area shall have a zinc coating thickness at least as thick as that required in ASTM A123/A123M for the material category. For best results, thickness measurements for the metallized coating should be taken with either a magnetic or an electromagnetic gauge.

      4. Site Repairs

         The preferred method of repair is by zinc metal thermal spraying. Due to the remoteness of most sites, however, and the unavailability of metal spraying equipment, repairs by zinc rich epoxy or zinc rich paint have to date generally been more popular.

         Site repairs should be limited to small coating defects and areas that have been cut or welded on site.

         Should excessive amounts of grease or oil be present at the affected area, it should be removed by means of an approved solvent. All residues are to be thoroughly removed by washing with clean water.

         The affected area should then be abraded with abrasive paper (roughness 80 grit) or alternatively thoroughly cleaned using, preferably a stainless steel brush. All dust and debris should be completely removed.

         Repair can now be carried out using an approved product.

         Single pack zinc rich paints are good materials and can easily be applied. They, however, require several coats to achieve a reasonable repair. Multiple coats will also necessitate longer drying times between coats.

         Until recently, the approved products for repair were only available in large containers. Due to the large quantities involved and short pot life when mixed, the products proved to be expensive and wasteful.

         Products are now available in two component form, packed for convenience in handy, easy to use squish packs. Two of these products are approved and available from the Hot Dip Galvanizers Association of Amerca and all of its members.

      1. DIFFERENT TYPES OF GALVANIZING DEFECTS AND THEIR REMEDIES & REPAIR METHODS

      The galvanized coating applied to steel is generally continuous, tough and of a thickness that will provide years of maintenance- free or low maintenance service.

      However, there are a number of common defects that arise in the galvanizing process. These are readily visible and have a variety of causes – many of which can be avoided through good communication and disciplined operations.

      The Australian Standard AS 4680:2006 – Hot Dipped Galvanized Coatings on Ferrous Articles, provides guidance regarding defects. It states that, galvanized coatings shall be:-

      • Continuous, and as smooth and evenly distributed as possible;

      • Free from defects that may affect the stated use of the article.

      • Free from blisters, roughness, sharp edges and flux residues.

Lumps and zinc ash are not permitted where they may affect the intended end use of the galvanized product. Visual inspection is the simplest and most important method to assess the quality of galvanized coatings.

A useful characteristic of the galvanizing process is that if the coating is continuous and has a satisfactory appearance; it will be sound and adherent.

The following Legends Indicates the category of Galvanzing Defects whether the HDG materials is accepeted or rejected as:

A Accept / R Rejected / N Negotiate / C Clean / REP Repairs

Responsibility Index: G Galvanized / D Designer / B Builder / Fabricator / S Steel Type / Surface

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REFERENCES:

Codes And Standards

1. ASTM A123 / A123M 2002: – Zinc (Hot-Dip galvanized) Coatings on iron and steel products.

2. ASTM A143 2014: – Practice for safeguarding against embrittlement of Hot-Dip Galvanized Structural Steel Products and procedure for Detecting Embrittlement.

3. ASTM A153 / A153M 2009: – Zinc Coating (Hot-Dip) on iron and steel Hardware.

4. ASTM A 36 / A36M 2008 Standards specification for Carbon Structural Steel.

5. ASTM A 384 2007:- Practice for safeguarding against warpage and Distortion during Hot-Dip Galvanizing Of steel Assemblies.

6. ASTM A 385 2011:- Practice for providing High Quality Zinc Coatings (Hot-Dip).

7. ASTM A 780 Repairs of Damaged Hot Dip Galvanizing Coatings

8. ASTM B6 2012 Standards Specification For Zinc.

9. ASTM E376 Practice for measuring coating thickness by Magnetic field or Eddy Current (Electromagnetic) examination Contains.

10. ASTM B201 Testing Chromate coatings on Zinc and cadmium surfaces.

11. ASTM A767 / A767M Zinc coated Galvanized steel bars for concrete Reinforcements.

12. AS/NZS 4680- 2006: – Hot Dipped Galvanized Coatings on fabricated ferrous Articles.

    Guides

13. American Galvanizers Asscoaitions Guides.

Practical experience during Factory inspection Services for Hot-Dip Galvanizing structural members.

14. Hot Dip Galvanizing for corrosion preventions (A specifiers guide).