The fastener industry should be made aware of an important recent development in the realm of. ASTM fastener standard specifications. ASTM F/. “ASME Hex Nut, 3/8 UNC-2B, SAE J Grade 5, ASTM F Zinc Coating ZN/FE Type 5B” we simply specify: “grade 5, zinc plated. ASTM F/FM: Standard Specification for Electrodeposited Coatings on Mechanical Fasteners, Inch and Metric.

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F — 00 Standard Speci?

ASTM / ASME spec F1941 for Zinc Plating … Which finish to choose?

A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval. The properties of the coatings shall conform to the ASTM standards for the individual? Coating thickness values are based on the tolerances for 1A and 2A external Uni? The coating must not cause the basic thread size to be transgressed by either the internal or external threads.

With normal methods for depositing metallic coatings from aqueous solutions, there asttm a risk of delayed failure due to hydrogen embrittlement for case hardened fasteners and fasteners having a hardness 40 HRC or above. Although this risk can be managed by selecting raw materials xstm for the application of electrodeposited coatings and by using modern methods of surface treatment and post heat-treatment bakingthe risk of hydrogen embrittlement cannot be completely eliminated.

Therefore, the application of a metallic coating by electrodeposition is not recommended for such fasteners. It also highlights the differences between barrel and rack adtm and makes recommendations as to the applicability of each process. The values given in parentheses are for information only. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Current edition approved Jan. Originally published as F — Last previous edition F — However, if not designated, signi? Ordering Information for Electroplating 5.

ASTM F – Portland Bolt

NOTE 1—Fasteners with a speci? See Section 10 and Appendix X1.

Thickness Designation 3 5 8 12 Minimum Thickness in. The appearance of corrosion products visible to the unaided eye at normal reading distance shall be cause for rejection, except when present at the edges of the tested fasteners. Refer to Annex A1 for neutral salt spray performance requirements for zinc, zinc alloy and cadmium coatings. Thick or thin local thickness in a location other than a signi? However the following restrictions apply: When such areas are subject to minimum thickness requirements, the purchaser and the manufacturer shall recognize the necessity for either thicker deposits on other areas or special racking.


ASTM F1941

Refer to Appendix X3 as a f11941 for the tolerances of the various thread sizes and classes asm the coating thickness they will accommodate. If the size of the fastener is large enough to economically use the rack-plating process, then the latter shall be used to obtain this thickness requirement.

If heavier coatings are required allowance for the deposit f191 must be made during the manufacture of fasteners. NOTE 2—With proper care many steel fasteners can be plated without baking by correlating process conditions to the susceptibility of the fastener material to hydrogen embrittlement, and by applying adequate process control procedures, such as those outlined in Appendix X4.

Test Method F is a recognized veri? Eight hours is considered a typical example of baking duration. Baking to relieve hydrogen embrittlement must be performed prior to the application of the chromate? Screw threads that are speci?

The other dimensional characteristics shall be as speci? It should be noted that modi?

Refer to Appendix X3 for further information on effects of coating on pitch diameter, allowances and tolerances for external and internal threads.

The test methods for determining the coating thickness are de? To secure uniformity of results, samples shall be aged at room temperature for 24 h before being subjected to the salt spray test. Refer to Appendix X1. In this process, quantities of an item are placed within a containment vessel, called a barrel. The barrel is designed to move the group of items, together, through each of the process steps, allowing ready ingress and egress of processing solutions and rinses. As the barrel is moved through the asttm steps, it is also rotated such that the individual items are constantly cascading over one another.

This can 6 damage the external threads of fasteners. The effect of thread damage is worse on heavy? In some of the process steps, notably the electrocleaning and electroplating steps, an electric current is applied to the group of items. Astj cascading action randomly exposes the surface of each individual piece to the process electrodes while also maintaining electrical continuity between all of the parts.

The local coating thickness on a part is a result of the electrical current density at that location. The extremities being the high current density areas receive the greatest coating thickness.

In contrast, the center or recesses such as xstm bottom of the threads, which are the low current density areas, receive the lowest coating thickness. This phenomenon is accentuated with increasing length and decreasing diameter of the screw or bolt. In this process, quantities of an item are placed on a support, called a rack. The rack is designed to move the group of items, together, through each of the process steps, allowing ready ingress and egress of processing solutions and rinses.


The electrical continuity is maintained between the parts by the rack itself. The average current density is usually low enough such that the extremity-to-center coating thickness ratio is much lower than with barrel-plating. The external thread damage is also minimized in comparison to barrel-plating due to the absence of tumbling.

Long screws and bolts have a length-to-diameter ratio greater than 5 but less than Special processing is normally required for bolts with a ratio greater than 10 in order to minimize the extremity-to-center thickness ratio. For internally threaded fasteners barrel-plating is generally suitable. Diameter Din. On an externally threaded fastener this occurs at the threaded tip. Measuring coating thickness on the threaded portion of a fastener is possible but impractical for in-process quality control veri?

For this reason the control mechanism speci? That standard should be consulted for more detailed information. Threaded Tip, 3 0. The external thread allowance may thus be used to accommodate the coating thickness on threaded fasteners, provided the maximum coating thickness is no more than 1? This applies to the following cases: It assumes that the external thread pitch diameter is at the maximum and that the internal thread pitch diameter is at the minimum of the tolerance see Fig.

High current densities increase hydrogen charging. Periodic inspections should be conducted according to a speci? The test plan should be designed based upon the speci? The testing frequency should initially establish and subsequently verify over time, the ability of a process to produce parts that do not have the potential for hydrogen embrittlement.

ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, f19941 entirely their own responsibility.

ASTM / ASME spec F for Zinc Plating Which finish to choose?

This standard is subject to revision at any time by the responsible technical committee and must be reviewed every? Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of g1941 responsible technical committee, which you may attend.

If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below. Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phonefaxor service astm.