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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The chromate finish letter E designates a black color. With normal methods for depositing metallic coatings from aqueous solutions, there is 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 suitable for the application of electrodeposited coatings t1941 by using modern methods of surface treatment and post heat-treatment bakingthe risk of hydrogen embrittlement cannot be completely eliminated.
ASTM / ASME spec F for Zinc Plating Which finish to choose?
It specifies coating thickness, supplementary hexavalent chromate or trivalent chromite finishes, corrosion resistance, precautions for managing the risk of hydrogen embrittlement and hydrogen embrittlement relief for high-strength and surface-hardened fasteners. For example, rather than specifying: That’s exactly what I needed.
My company uses fasteners in the most simple sense–like the kind of fasteners you buy in the bulk bin at the local hardware store. 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 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.
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.
Nonmagnetic Coatings on Magnetic Basis D1941. NOTE 1—Fasteners with a speci? The coating material, coating thickness, chromate finish, and trivalent chromite finish shall be selected and designated.
My research is leading me to believe that ASTM F M both inch and metric are the two standards I need; but even those have over grades listed! Long screws and bolts have a length-to-diameter ratio greater than 5 but less than A superscript epsilon e indicates an editorial change since the asstm revision or reapproval.
See Section 10 and Appendix X1. Toby — Thanks for boiling it down for me. The electrodeposited coating shall cover all surfaces and shall meet the following requirements: Thank you for your assistance. In contrast, the center or recesses such as the bottom of the threads, which are the low current density areas, receive the lowest coating thickness.
ASTM F – Portland Bolt
The electrical continuity is maintained between the parts by the rack itself. 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. 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?
The values given in parentheses are for information only. December 9, Q. 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. If heavier coatings are required allowance for the deposit buildup must be made during the manufacture of fasteners.
That standard should be consulted for more detailed information. This abstract is a brief summary of the referenced standard. Work Item s – proposed revisions of this standard.
All information presented is for general reference and does not represent a professional opinion nor the policy of an author’s employer.
For this reason the control mechanism speci? 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. Historical Version s – view previous versions of standard.
Test Method F is a recognized veri? Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.
Threaded Tip, 3 0. Special processing is normally required for bolts with a ratio greater than 10 in order to minimize the extremity-to-center thickness ratio. This standard astk subject to revision at any time by the responsible technical committee and must be reviewed every? The external thread damage is also minimized f19941 comparison to barrel-plating due to the absence of tumbling. This standard does not purport to address all of the safety concerns, if any, associated with its use.
Eight hours is considered a typical example of baking duration. As the barrel is astk through the process steps, it is also rotated such that the individual items are constantly cascading over one another. My follow up question would be, if the fasteners are coated with trivalent chromite adding the designation “T”why do the salt spray hours f941 the ASTM spec differ between any color chromate designation?
The cascading action randomly exposes atm surface of each individual piece to the process electrodes while also maintaining electrical continuity between all of the parts. Current edition approved Jan.