This standard is issued under the fixed designation A/AM; the number 1 This practice is under the jurisdiction of ASTM Committee A05 on Metallic-. A / AM() Standard Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural Steel Products Format, Pages, Price. PDF. ASTM A - Download as PDF File .pdf), Text File .txt) or read online. ASTM A
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ASTM A pdf - Download as PDF File .pdf), Text File .txt) or read online. ASTM Standards A/AM Practice for Safeguarding Against Embrittle- 2 For referenced ASTM standards, visit the ASTM website, aracer.mobi, or. ASTM A - Designation: A – 01 Standard Practice for Safeguarding Against Embrittlement o.
Testing Mats. Published December Origi- 5. Last previous edition A — 74 Reapproved These criteria generally depend on the bility of the designer and fabricator. The galvanizer shall direction of grain, strength, and type of steel.
A cold bending employ proper pickling and galvanizing procedures. Testing for Embrittlement of Steel Shapes, Steel ensure satisfactory properties in the final product. Although Castings, Threaded Articles, and Hardware Items sharper bending on thin sections can usually be tolerated, 8.
If one test specimen If the design requires sharper bending than discussed herein, should be found embrittled by these tests, two additional the bending should be done hot, or if done cold the material specimens should be tested.
Failure of either the second or the should be subsequently annealed or stress relieved as noted in third specimen shall be cause for rejection of the lot see Note 5. Unless otherwise agreed upon by the manufacturer and annealing or stress-relieving. For test by purchaser after delivery, the lot consists of the metal removed from the periphery of the hole after punching, single order or the single delivery load, whichever is the smaller, unless or shall be drilled, or thermally treated prior to galvanizing as the lot identity, established in accordance with the above, is maintained noted in 5.
However, if required, proper thermal treatment shall reinforcing bars, etc. For heavy cold deformation comparing the degree of bending to that which is obtained on exemplified by cold rolling, sheared edges, punched holes, or a similar ungalvanized article.
In the case of previously bent articles such as forming, etc. The the ungalvanized article. For of section thickness. After cutting, the cut surface 8. Preparation for Galvanizing and ungalvanized samples compared. Regardless of the appearance, the tube. The stresses in the steel from processing affect the all of these products have an equal amount of corrosion intermetallic formation and can result in this striped look.
The corrosion protection is not affected thus these parts meet the specification. Figure 9: Shiny vs. In Figure 10, the outer The hot-dip galvanized coating can have various surface edges of the product were cooled rapidly, allowing a free defects that may or may not lessen the long-term corrosion zinc layer to form on top of the intermetallic layers.
The performance. Some of these surface defects are rejectable, as center of the product remained above F longer and the they can decrease the corrosion protection, while others will metallurgical reaction between zinc and iron continued in have little or no effect on the corrosion performance and are the solid state consuming the free zinc layer, resulting in a acceptable according to the specification. As the product weathers, the differences in appearance will become less noticeable and the overall color Bare Spots will turn a uniform, matte gray.
Bare spots, uncoated areas on the steel surface, are a surface defect that can occur because of inadequate surface preparation. Bare spots may be caused by welding slag, sand embedded in castings, excess aluminum in the galvanizing kettle, or lifting devices that prevent the coating from forming in a small area. In order to avoid bare spots, Figure 12 , the galvanizer must ensure the surfaces are clean and without rust after pretreatment. Small bare spots can be repaired in the galvanizing shop.
If the size of the bare spot or total number of spots causes rejection, the parts may be stripped, regalvanized, and then re-inspected for compliance to the specifications.
It is caused by incorrect abrasive blasting procedures creating shattering and delamination of the alloy layers in the zinc coating. Blasting damage Figure 13 can be avoided when careful attention is paid to preparation of the product for painting. Since blasting damage is induced by a post-galvanizing process, the galvanizer is not responsible for the damage. Lifting devices can leave uncoated areas on the finished product that will need to be renovated.
Superficial marks Figure 14 left on the galvanized coating from the lifting attachments are not grounds for rejection unless the marks expose bare steel; in such a case, the galvanizer must repair the bare areas before the part is acceptable.
A good example is the screen shown in Figure 15a. Similarly, clogged threads are caused by poor drainage of a threaded section after the product is withdrawn from the galvanizing kettle. Clogged threads must be cleaned and free of excess zinc before the part will meet the specification. There are a number of causes for zinc peeling. Many large galvanized parts take a long time to cool in the air and continue to form zinc-iron layers after they have been removed from the galvanizing kettle.
This continued coating formation leaves behind a void between the top two layers of the galvanized coating. If there are many voids formed, the top layer of zinc can separate from the rest of the coating and peel off the part. If the remaining coating still meets the minimum specification requirements, then the part is acceptable. If the coating that remains on the steel does not meet the minimum specification requirements, then the part must be rejected and regalvanized.
If delamination, Figure 16 occurs as a result of fabrication after galvanizing, such as blasting before painting, then the galvanizer is not responsible for the defect.
Distortion occurs when steel tries to move to accommodate thermal expansion. Since the steel is welded in place it cannot move. This creates a high stress level often relieved by distortion of the part. Distortion is acceptable, unless it prevents the part from fulfilling its intended use.
Many distorted thin steel sheets can be bent after galvanizing to bring the part to an acceptable final condition. Figure Distortion Acceptable Drainage Spikes Drainage spikes or drips are teardrops of zinc along the edges of a product. These are caused when steel products are removed from the galvanizing kettle horizontally preventing proper drainage of the zinc from the surface Figure Drainage spikes are typically removed during the inspection stage by a buffing or grinding process.
Comprised of excess zinc, drainage spikes and drips will not affect corrosion protection, but are potentially dangerous for anyone who handles the parts. Therefore, these defects must be removed before the part can be accepted. Dross Inclusions Dross inclusions are a distinct particle of zinc-iron Figure Drainage spikes intermetallic alloy that can become entrapped or entrained in the zinc coating Figure Dross inclusions may be avoided by changing the lifting orientation or redesigning the product to allow for more effective drainage.
If the dross particles are small and completely covered by zinc metal, they will not affect the corrosion protection, and thus, are acceptable. If there are gross dross particles large inclusions that prevent the full galvanized coating from forming on the steel, then the particles must be removed and the area repaired. One common additive is aluminum, which helps with the aesthetic of the coating.
When excess aluminum is in the galvanizing bath, it creates black marks or bare spots on the surface of the steel Figure Bare spots due to excess aluminum in the bath may be repaired if only small areas are evident; however, if this condition occurs over the entire part, it must be rejected, stripped, and regalvanized.
Excessively thick coatings generate high stresses at the interface of the steel and galvanized coating which causes the zinc to become flaky and separate from the steel surface Figure If the area of flaking is small, it can be repaired and then accepted; however, if the flaking area is larger than allowed by the specifications, the part must be rejected and regalvanized. Figure Flaking rejectable Flux Inclusions Flux inclusions are created by the failure of the flux to release during the hot-dip galvanizing process, preventing the coating from forming.
Because no coating grows under the inclusion, the area must be repaired prior to acceptance. Flux deposits on the interior of a hollow Pipe Rejectable part, such as a pipe or tube, Figure 22 cannot be repaired and thus must be rejected. Parts rejected for flux deposits may be stripped of their zinc coating and then regalvanized to provide an acceptable coating. Oxide Lines Oxide lines are light colored film lines on the galvanized steel surface created when a product is not removed from the galvanizing kettle at a constant rate Figure The inconsistent rate of withdrawal may be due to the shape of the product or the drainage conditions.
Oxide lines will fade over time as the entire zinc surface weathers oxidizes. Strictly an aesthetic condition, oxide lines have no effect on the corrosion performance; and therefore, are not a cause for rejection of hot-dip galvanized parts. This can occur when many small products are hung on the same fixture, creating the chance products may become connected or overlapped during the galvanizing process Figure The galvanizer is responsible for proper handling of all steel parts in order to avoid defects Figure Products in Contact Figure Touch Marks from products in contact.
A similar type of surface defect, touch marks are damaged or uncoated areas on the surface of the product caused by galvanized products resting on one another or by the material handling equipment used during the galvanizing operation. Touch marks Figure 25 are cause for rejection, but may be repaired if their size meets the specification requirement for repairable areas.
Rough Surface Condition Rough surface condition or appearance is a uniformly textured appearance over the entire product Figure Rough surface Condition Acceptable condition can actually have a positive effect on corrosion performance because a thicker zinc coating is produced; and therefore, rough coatings are usually not cause for rejection.
However, one of the few situations where rough coating is cause for rejection is on handrails, as it impacts the intended use of the product. Runs Runs are localized thick areas of zinc on the surface that occur when zinc freezes on the surface of the product during removal from the zinc bath Figure Runs are not cause for rejection unless they affect the intended use of the steel part.
If runs are unavoidable due to the design of the product, but will interfere Figure Runs Acceptable with the intended application, they can be buffed. Rust Bleeding Rust bleeding appears as a brown or red stain that leaks from unsealed joints after the product has been hot-dip galvanized Figure It is caused by pre-treatment chemicals that penetrate an unsealed joint.
During galvanizing of the product, moisture boils off the trapped treatment chemicals leaving anhydrous crystal residues in the joint. Over time, these crystal residues absorb water from the atmosphere and attack the steel on both surfaces of the joint, creating rust that seeps out of the joint. If bleeding occurs, it can be cleaned up by washing the joint Figure Rust Bleeding acceptable after the crystals are hydrolyzed. Bleeding from unsealed joints is not the responsibility of the galvanizer and is not cause for rejection.
Sand Embedded in Castings Sand inclusion defects occur when sand becomes embedded in castings and creates rough or bare spots on the surface of the galvanized steel Figure Strain-aging refers to the delayed galvanized after fabrication, and outlines test procedures for increase in hardness and strength, and loss of ductility and detecting embrittlement.
Conditions of fabrication may induce impact resistance which occur in susceptible steels as a result a susceptibility to embrittlement in certain steels which can be of the strains induced by cold working. The aging changes accelerated by galvanizing. The indication that no embrittlement problem is to be expected for susceptibility to hydrogen embrittlement is influenced by the those steels, processes, and galvanizing procedures. In the case of galvanized steel, the acid as the standard.
However, the heat of the galvanizing bath safety concerns, if any, associated with its use.
It is the partially expels hydrogen which may have been absorbed. In responsibility of the user of this standard to establish appro- practice hydrogen embrittlement of galvanized steel is usually priate safety and health practices and determine the applica- of concern only if the steel exceeds approximately ksi bility of regulatory limitations prior to use. Terminology 3. An embrittled product characteristically fails by fracture and is accentuated by areas of stress concentration such as without appreciable deformation.
Types of embrittlement usu- caused by notches, holes, fillets of small radii, sharp bends, etc. The rate at which this temperature loss of ductility occurs 1 varies for different steels. The expected service temperature This practice is under the jurisdiction of ASTM Committee A05 on Metallic Coated Iron and Steel Products and is the direct responsibility of Subcommittee should thus be taken into account when selecting the steel.
Prepared by Subcommittee A See Proceedings, Am. Testing Mats.
Published December Origi- 5. Last previous edition A — 74 Reapproved These criteria generally depend on the bility of the designer and fabricator.