Rust Protection - Grating Clamps

[ride5150]

I'm considering using regular saddle clips and field drilled holes, or clamp-style grating clips for securing grating panels. My concern is with long-term rust protection, as the grating and framing members will all be hot dip galvanized. in my situation, making a call on this is within my scope.

if the erector field drills holes, the galvanizing will naturally be removed within the hole. I can tell them to touch up holes with a cold galvanizing compound and ensuring it is fully cured prior to bolt installation. not sure how well this works.

if i used clamp-clips, i'm concerned that the clip "teeth", or serrations, that bite into the underside of the beam flange will also damage the finish. Lindapter makes one without teeth, but i still have concerns.

how have you handled this on similar projects?

 

[KootK]

You should be fine with both options. Galvanizing is nowhere near as sensitive to localized removal as you are imagining. Zinc, even some distance from the exposed substrate, will still offer galvanic protection to that substrate. This is precisely why galvanized rebar is often preferred over epoxy coated rebar in high durability applications. Sure, it's good practice to tough up the exposed bits when that's fairly simple to do. I wouldn't sweat it for bolt holes and the like though.

 

[canwesteng]

Won't the bolts or the teeth also be galvanized? Like kootk said, that is what makes galv great, little nicks aren't all that critical. The only environment I'd be concerned about this is one where I wouldn't use galvanizing.

You can also use Hilti clips, they have stainless pins that are impact welded to the supporting member, so no damaged surface is left exposed. Though in harsh exposures mixing stainless and galv is worse still

 

[HTURKAK]

how have you handled this on similar projects?

My experience is mostly at oil and gas industry. When the method of fastening grating requires field drilling or welding, which destroys the protective coating the affected area would be repaired using an organic zinc rich coating. And this was mandatory requirement for the projects that i have involved.
If the grating is not open to air and there is no risk of washing of stains with rain water , may be you can relax this requirement.

 

[human909]

Nicks and scratches in galvanised coatings don't matter in NORMAL applications for the reason Kootk mentioned. Half the reason why a cold gold galling or hot stick galling is done is for aesthetic reasons to keep client happy and not show up your site rectifications.

Now in harsh environments this may not be the case. HTURKAK's experience might pedantry of the industry or because they are costal or sea based structures exposed to salt water. This is an entirely different beast to steel not exposed to salt water.

The other harsh environment I've encountered that isn't chemical related is bureaucratic pedantic nonsense. And they can be brutal on any engineer, project manager or the sanity of anybody involved.

 

[dvd]

Galvanizing Repair - Structural engineering general discussion

Does anyone have experience with field repairs of galvanized steel due to welding, abrading, etc.? Can you add any specifications if any?

www.eng-tips.com

Touch-Up and Repair

The touch-up and repair of hot-dip galvanized steel coatings is important to maintain uniform barrier and cathodic protection as well as ensure longevity. ASTM A780 Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings contains three acceptable methods of touch-up…

galvanizeit.org

https://galvanizeit.org/uploads/publications/Touch-Up_Repair_Suppliers_HDG-2023.pdf