This standard is issued under the fixed designation F ; the 1 This specification is under the jurisdiction of ASTM Committee F16 on. ASTM: F – Standard Specification for Chromium/Zinc Corrosion Protective Coatings for Fasteners. 1. Scope This specification covers the basic. ASTM F/FM Standard Specification for Zinc/Aluminum Corrosion Protective Coatings for Fasteners. standard by ASTM.
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High Strength Bolts Coatings – Portland Bolt
Due to hydrogen embrittlement concerns ASTM recommends against hot-dip galvanizingmechanical deposition, or electroplating with zinc or other metallic coatings on high strength bolts ultimate tensile strengths that exceed ksi.
So what are the alternatives to provide corrosion resistance for A structural bolts? Protective Coatings ASTM recommends that if a protective coating is required for A bolts, one of two approved coatings is recommended. This fastener wstm made from weathering steel which is inherently corrosion resistant. However, these fasteners are not as readily available in the marketplace as A Type 1. F Grade 3, commonly known as Dacromet.
Jovito- We would be happy to quote your specific bolting needs if you want to send us a list of the bolts you are looking for. Hello, We have specified A Dracomet coated bolts for a telecommunications monopole in Canada. They were used to in flange type splices of two tubular monopole sections.
One year after installation adtm bolts are rusting. Is the coating that fragile? Serge- We have very little experience with Dacromet coating. We are not sure how fragile the coating is during installation.
Parham- We cannot make specific recommendations, but I can say that painting A bolts is quite common. Hi, Recently we were informed that Dacromet coating is being phased out. Since we are using A bolts in our structure, we have to propose a replacement.
But there are some doubts.
The bolts and nuts are already coated with Dacromet and the proposal is to coat the DTI washers with Magni Since the Dacromet and Magni will be in contact with one another, Are they compatible with one another? Since the bolts are pre-tensioned, will there be any issues with Magni with regard to pre-tensioning i. Bandana- There are no issues mixing coatings with DTI washers.
High Strength Bolts Coatings
It is required that the bolt and nut are coated by the same process, but the washer can be an alternate coating. We also see no issues with pre-tensioning. Is fluorocarbon coating acceptable to A bolts for corrosion prevention? I suppose they are similar to painting. That said, I do not know much about aatm coatings and how they are applied. A coatings engineer may choose to allow an exception in some cases, but ASTM will not officially sanction any coatings that are not approved by the F16 committee.
We assumed that the properties on the bolts is not affected satm the final tension might be change? If so, did the tension will be higher? Pierre-Paul — The properties of the bolt and the final tension should not be impacted. The asfm torque may vary from plain finish or other coatings, but the bolt should still function the same.
I do not have any friction coefficient information on Magniso I do not know how much the torque will be affected. Aastm hot-dip galvanize provides high thickness level barrier protection 2 mils for substrates, it is not approved for use on high strength bolts because hot dip galvanize is susceptible of hydrogen embrittlement and cracking of fasteners that can result out in c1136 field. I am using A grade BC and need a smooth finish with minimal irregularities.
Your first question, is it appropriate to specify ASTM F Grade 3would be best answered by an engineer familiar with the coating and the application.
Depending on the amount of corrosive forces at work in the application, F may be sufficient, but it may not. Normally where I see F specified is in applications with higher strength fasteners that cannot be hot-dip galvanized, such as ASTM A heavy hex bolts.
The corrosion protection offered by F in those cases would be superior to nothing at all. As for the thickness of both coatings, F grade 3 specified a coating thickness of 0.
Hot-dip galvanized hex nuts are therefore tapped oversize to accommodate the thick coating, whereas F specifically states that the thread fit shall not be adversely affected. Your email address will not be published. Leave this field empty.
What corrosion-resistant coatings are available for high-strength over ksi bolts? Consulting a structural engineer involved on the project is always the best solution. Leave a Reply Asstm reply Your email address will not be published.