ASTM A325 Bolts - Chrome Plated or similar finish

[PT999]

I just come from a job site where ASTM A325 have been used, not tension controlled type, and they are chrome plated or some kind of shiny finish, and marked H H H - ASTM A325. I am going to ask for the paperwork, but I though I'd ask here if this is OK.

 

[JLNJ]

Are they galvanized?

 

[PT999]

No, if they were galvanized the finish would be a dull gray. These do not look galvanized.
They look more the finish for bolts you can get at a hardware store, but those are Grade 2, 5 or 8.

These bolts are marked A325, so that's my concern.

 

[Ron]

The only two finishes I've ever seen on A325 bolts were plain (no finish) and hot dipped galvanized. I suppose those could be cadmium or similar electroplating; however, those would be special order. Usually the only two markings on the head are A325 (+ special use/application designations like "X") and the manufacturer's designation. The HHH could have to do with the manufacturer. Coincidentally it could mean "Heavy Hex Head" which all A325's must have, but see no reason to designate that.

 

[hokie66]

Hard to say, without seeing them. Galvanized bolts, when new, are not dull gray, but they don't look chrome plated, either. Best guess is zinc electroplated. You might try to find out where the bolts came from, as that would give a clue. Bolts come from all sorts of countries now, some with less quality control than we expect. If Chinese, they do a lot of electroplating.

 

[ajh1]

Sounds like electroplating.

 

[azcats]

I agree that they're probably zinc plated.

 

[PT999]

Well lets say its electroplated or zinc plated - Is this legit for a structural connection as per AISC, RCSC, etc.

 

[IFRs]

From an older 2002 version of A-325, not sure what the most recent version says ( best if you by one ):

4.3.1 When zinc-coated fasteners are required, the purchaser
shall specify the zinc coating process, for example, hot
dip, mechanically deposited, or no preference.

4.3.2 When hot-dip is specified, the fasteners shall be
zinc-coated by the hot-dip process and the coating shall
conform to the coating weight/thickness and performance
requirements of Class C of Specification A 153.

4.3.3 When mechanically deposited is specified, the fasteners
shall be zinc-coated by the mechanical deposition process
and the coating shall conform to the coating weight/thickness
and performance requirements of Class 50 of Specification
B 695.

4.3.4 When no preference is specified, the supplier shall
furnish either a hot-dip zinc coating in accordance with
Specification A 153, Class C, or a mechanically deposited zinc
coating in accordance with Specification B 695, Class 50.
Threaded components (bolts and nuts) shall be coated by the
same zinc-coating process and the supplier’s option is limited
to one process per item with no mixed processes in a lot.

4.4 Lubrication—When zinc-coated nuts are ordered with
the bolts, the nuts shall be lubricated in accordance with
Specification A 563, Supplementary Requirement S1, to minimize
galling.

 

[CELinOttawa]

Hokie: Didn't Aussie have a rash of counterfeit bolts out of China? Always makes me nervous when I see something wholly out of the norm!

 

[hokie66]

Yes, you are correct. Some of them have been found to be very substandard.

 

[connectegr]

Other than a seller's sample, I have never seen an electroplated structural bolt, A325 or A490. I don't know why someone would prefer the expense. I would recommend verifying the intent and don't skip pre-installation verification.

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[xian555]

Hello PT999,

This might be coming a little late in the conversation but here's one definite possibility:

a) galvanization recipes vary from one shop to another, but also from one client type to another.

b) when the galvanization recipe includes more ALUMINUM is provides a very nice finish, close to what a chrome plating would be. This hot-dipped galvanizing recipe is reserved for consumer products, where aesthetics are more important than durability, and where the product life cycle is expected to be shorter. For industrial projects where life cycle projects are expected to have a longer life they will put minimal aluminum and more zinc. The finish is a dull grey but has a significantly longer life. Note that this is because aluminum oxidizes more readily than zinc.

Occasionally there is a mix up in hot dipped galvanization and customer don't get what's expected, especially if they didn't specify anything.

 

[ajh1]

Zinc eletroplating per ASTM F1941 is not that uncommon for A325 bolts. We use the treatment for bolts connecting our secondary framing members which have a G30 finish on them. It provides an appearance similar to the galvanized finish and also helps eliminate rust streaking on the steel from the bolts if they are left exposed for a short period of time. The finish is not equivalent to a full galvanized surface for long-term corrosion protection. The other advantage of the electroplating is that because it is a very thin coating there is no need to overtap nuts the way that is required when you are doing full galvanizing.

 

[connectegr]

ASTM A325 does not allow electoplating as an approved coating. Hot dip galvanized and mechanical zinc coating only.

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[tbuelna]

You can get a "shiny" finish from bright electroplated zinc. This is the finish you would see on the cheap bolts in the bins at your local hardware store. However, while it is low cost and easy to apply in mass production, it is thin and does not provide good corrosion protection.

 

[hokie66]

connectegr,

Does the specification actually prohibit electroplating, or just doesn't mention it? They are probably just considered as plain black bolts, as the electroplating does little to achieve corrosion resistance.