ASTM A153 and ASTM F2329 are similar specifications for galvanizing of spin-on hardware after galvanizing, although F2329 does not cover galvanizing of nails or rivets. Galvanizing fasteners according to A153 usually meets or exceeds the requirements of F2329, as it references A153 in many sections. However, there are some differences between the specifications that the galvanizer and the customer should be aware of to determine whether it is practical for a particular galvanizing plant to meet the customer's specific requirements under the latest revision of F2329 (2015).
The main differences between the two specifications, described below, include issues related to sampling protocol, coating thickness, inspection, brittleness, and documentation.
Sampling Protocol: Lot Lots vs. Production Lots
ASTM F2329 describes two different sampling plans for production lots and batch lots. In addition, there are two types of production batches: Production Batch Detection Process and Production Batch Prevention Process. Differences in lot types lead to different sampling plans, which specify the number of test items to perform various test methods during inspection of the finished product. It is important to ensure that the customer specifies what type of lot is required. The F2329 standard defines the two different lots and their associated sampling plans as follows:
Batch batches
A batch is defined as a quantity of identical parts cleaned, pickled, cast and galvanized at one time in a galvanizing basket. Table 1 of F2329 provides the sampling plan for the lots. The lot inspection process is more similar to inspection under A153 than to production lot inspection, but Table 1 of F2329 has some additional requirements to consider. See extract from Table 1 below.
There are three columns listing the number of test items for three different inspection tests required under F2329: coating thickness, adhesion, and appearance. Compared to the A153 sampling plan, F2329 requires fewer samples per lot size, but the galvanizer must also perform adhesion testing and visual inspection of the appearance of these test articles, as defined in the table 1. It is important to note that the acceptance criterion in all cases is zero defects.
Production batches
Production batches are defined as batches of parts from the same manufacturing batch, processed continuously through cleaning, pickling, casting, dipping in molten zinc and centrifuging, or other means, without any significant change. in time, temperature and concentration of the components of the process. There are two types of production lots, one for a detection process and another for a prevention process. For each of these types, there are also inspection criteria for coating thickness, visual appearance and adhesion. The acceptance number in all cases is zero defects. To determine how many samples are needed to check conformance based on lot size, F2329 refers to Table 3 of F1470, Practice for Sampling Fasteners for Specified Mechanical Properties and Performance Inspection.
Note A: Suppliers must provide the results of the certified tests from which the shipping lots come. If certified test reports are not available, the supplier must default to sample size C and perform the required tests.
The process type of the production lot will determine which column should be referenced for the sample size of each inspection criterion, as summarized in the table below, or according to the F2329 sampling plan flowchart. For example, a lot size of 500 items under the screening process requires testing 11 samples for coating thickness, 11 samples for visual appearance, and 3 samples for adhesion.
Inspection
Under F2329, coating thickness inspection is performed in accordance with Practice E376, which is the same method required by ASTM A153. In accordance with Note C of Table 1, sample testing for coating thickness is only required to be carried out once every five batches. For long pieces (anchor bars or items over five feet in length), coating thickness measurements should be made at each end and in the center of the item. This method is similar to inspecting coating thickness on multi-sample items galvanized to ATSM A123. This additional form of inspection is not required per ASTM A153.
Adhesion testing is not normally performed when galvanizing per the requirements of A153 unless there is evidence of an adhesion problem, but F2329 requires that adhesion testing (robust blade test) be performed for the number of items listed. in Table 1, and for each lot.
Appearance and smoothness test methods according to F2329 shall be carried out for each lot by visual inspection in accordance with the methods provided in A153.
For materials that do not conform to the test methods required in F2329, it is necessary to reference and use paragraph 8 of ASTM F1470, Practice for Sampling Fasteners for Specified Mechanical Properties and Performance Inspection, for lots not compliant.
Coating thickness
Table 2 of F2329 lists the average coating thickness requirements for production lots, batch lots, and individual samples. A summary of the numerical differences between the two specifications related to coating thickness requirements for all materials is presented in the table: Zinc Coating Thickness Requirements: ASTM A153 vs. F2329. The coating thickness requirements of Table 1 of A153 meet or exceed those of Table 2 of F2329, except for
Fasteners and nuts 3/8 inch or less in diameter: The average coating thickness on individual samples per F2329 is 1.5 mils, which is greater than the 1.4 mils required by A153.
Washers less than 3/16 inch thick: The average coating thickness on individual samples per F2329 is 1.5 mils, which is greater than the 1.4 mils required by A153.
A394 Grade Bolts: ASTM F2329 contains Supplemental 1 requirement for the minimum average coating thickness on A394 bolts (2.8 mils average for all samples and 2.5 mils for individual samples), which is significantly greater than that required by standard A153. In ASTM A153, these bolts would be included in the Class C coating thickness requirements (2.1 mils average for all samples and 1.7 mils for any individual sample).
Minimize fragility
Both ASTM A153 and F2329 outline two methods for preventing hydrogen embrittlement: baking after pickling and before galvanizing, or abrasive blasting and flash pickling before galvanizing. If a brittle test is required per ASTM A153, it must be performed per paragraph 9 of A143. On the other hand, if it is necessary to perform a brittle test according to F2329, it must be performed according to ASTM F606 (a wedge placed and tensioned under the head of the screw), which is a different method than any of the methods described in paragraph 9 of standard A143. Each bolt specification may list additional methods to prevent hydrogen embrittlement, as well as establish additional requirements for brittle testing that must be investigated separately.
Mechanical tests and bath temperature recording
The temperatures used in the hot-dip galvanizing process do not usually appreciably alter the mechanical properties of the steel, but there are some cases where problems can arise. These cases may include when the steel has been severely work hardened or when the temperature of the galvanizing bath exceeds the stress relief or tempering temperatures of the fasteners. Fasteners subjected to strong strain hardening must be stress-relieved before galvanizing. Paragraph 7.2.1.2 of F2329 requires the purchaser to arrange for mechanical testing to be performed after galvanizing if the temperature of the galvanizing bath (indicated as 820-900 F) is higher than the stress relief or cooling temperatures. tempered.
It is necessary for the galvanizer to communicate the bath temperature to the customer to ensure that the end user understands the effects the galvanizing temperature will have on the steel. If specified by the customer, the galvanizer shall provide the average galvanizing temperature to which the fasteners will be exposed. Best practice is to note the bath temperature when galvanizing steel according to F2329, although only the average bath temperature is required.
Cooling
According to paragraph 5.3.1 of F2329, all parts must be water quenched, unless the customer specifies air quenching to prevent the formation of zinc oxide. Additionally, paragraph 5.5.1 allows the customer to request post-treatment, such as chrome plating to reduce the potential for wet storage stains, or phosphating to assist post painting. Since A153 does not require water quenching or chemical aftertreatments, it is necessary for the customer and the galvanizer to agree to determine if the galvanizer has a quench tank and the ability to perform chemical aftertreatments, or if it is acceptable. cooling with air.
Lubrication
ASTM A153 does not require lubrication of hot-dip galvanized fasteners, but paragraph 5.5.2 of F2329 allows the customer to request lubrication of nuts, bolts, or screws to improve assembly. Therefore, it should be clarified whether the plant has the ability to lubricate the hardware after hot-dip galvanizing. Otherwise, it will be necessary for a third party to apply the lubricant at an additional cost.
Delivery and documentation
ASTM F2329 requires more detailed ordering information from the customer and more documentation from the galvanizer at the time of delivery than does ASTM A153. The amount of additional documentation beyond the requirements of ASTM A153 will vary based on a number of optional requirements that the customer may specify in F2329. However, if a buyer also requires the galvanizer to inspect the dimensional requirements of the parts at the time of delivery, the buyer will need to provide the galvanizer with the necessary inspection gauges and tools.
