Metallizing Question

By Mikeqc1 (****)

Date 06-30-2009 14:06

What state? Massachusetts?

By qcmike

Date 06-30-2009 14:40

Yes, but it is not MHD. I actually talked to MHD and they said it was a good question but did not have any experience in this situation. It's our first Metallizing project and I want to make sure it goes smoothly. I would expect they want metalizing on the bolt surface. But I wanted to check if this was common practice or specified somewhere. The owner is looking to us for guidance. Any help?

By Mikeqc1 (****)

Date 06-30-2009 14:47

MAINE DEPARTMENT OF TRANSPORTATION
506.33 TSC Requirements The coating thickness shall be between 14 mils and 17 mils. The
DFT on faying surfaces shall not exceed the thickness tested for Class B slip coefficient rating.

I think this is from CA DOT
. The seal coat shall not be applied to faying (contact) surfaces of bolted connections.

http://www.dot.ca.gov/hq/esc/oe/specifications/SSPs/2006-SSPs/Updates/2007-09_updates/59-565_E_B09-21-07.doc

Do you have the MA specs?
What about contract docs?
ASHTTO?
I look more later.

TSC can be tricky at first. ill post more links later.
MDK

By qcmike

Date 07-01-2009 20:40

Great Link MDK!! Thanks. That's exactly what I was looking for. I knew it had to be somewhere. The CA Spec. backs up my response to only apply metalizing to the faying surfaces as long as it meets class B. Perfect!!

By HgTX

Date 06-30-2009 14:48

Are you handling metallizing in both shop and field?

Hg

By qcmike

Date 06-30-2009 15:35

We are sub-contracting the metalizing. It will be applied in a shop either in-house or outside.

The owner is questioning our "no paint" notes on the drawing. I need to provide a clarification. But, I'm leaning toward putting it back on them. I'm sure a consultant sold them on the metalizing in the first place. They should be able to provide an answer. I'd hate to steer them down a path and then have a problem.

By HgTX

Date 06-30-2009 16:53

I don't know much about metalizing on faying surfaces, but I do know something about paint, and "no paint" is probably exactly right if those are slip-critical connections. Your client needs to be able to provide the information about whether the bolted connections are slip-critical and, if so, what class they assumed in the design. Almost surely the paint can't provide the required slip resistance; topcoats typically don't. (For the metallizing, it's probably as good as a roughened galvanized surface, Class C (similar to Class A), but I don't know that for a fact.) They'll have to find a way to get those connection areas painted in the field.

If they're shear/bearing (non-slip-critical) connections, then painting the whole thing is probably fine.

There's a lot of good information in the RCSC Bolt Spec:
http://boltcouncil.org/files/2004RCSCSpecification.pdf

Hg

By Mikeqc1 (****)

Date 06-30-2009 14:59

In the july welding journal there is a load of information to help you.

By qcmike

Date 06-30-2009 15:35

thanks. Does that need I need to pay my dues?

By Mikeqc1 (****)

Date 06-30-2009 16:08

you were not supplied special provisions?
Do you have the MA spec book?
I can remember that some states did not want sealer on some surfaces.
MDK

By qcmike

Date 06-30-2009 17:01

Thanks all to the great tips.

By michael kniolek (***)

Date 06-30-2009 21:39

I worked in a Bridge bearing shop QA for many years, and found each state had an idea of what was best.
Some wanted primer only, some wanted just a rust preventive mist, some wanted nothing at all.
but never a 2nd or 3rd coat.
I’m wondering if this is your first time using this metalizing facility have you reviewed the process used.
I would always do tests for each state inspector.
I test the operator , do an adhesion pull, bend and cut test. (they don’t always pass)
I would look at the process closely, metalizing is great protection, but if its new to the facility there are many ,many, many things that can cause failure.
I would be required to produce Humidity readings twice a day , a profile strip and the inspection reports for endless DFT readings.
All documented.
Once I was away for a few days from the shop so management in their infinite wisdom decided to wheelabrate only.
so 30 plates all done and coated sitting in the shop ready to go when I come in..
First thing I do is grab a bolt to check the thread condition after coating, it didn’t fit so I figure its got metalizing inside. I grabbed the Air hose to blow it out and *%#^* the coating came off in a huge sheet.
I pulled as much of it off as I could before telling them......I wanted them all reblasted and resprayed.

Just make sure they KNOW what they are doing and whats expected for a coating on a bridge.

By qcmike

Date 07-01-2009 20:34

Thanks Mike.

It is our first rodeo with Metalizing but I am familiar with the process. We are subcontracting the metalizing to a qualified outfit. The spec's require a 5 year minimum. What the spec's don't discuss is what to do at the faying surfaces.

Thanks for the war story. I've heard surface prep. is critical to a good job. We wanted it galvanized anyways!!

By qcmike

Date 07-01-2009 20:36

Special provision cover the system not faying surfaces on slip critical connections. Normally, zinc primer only. I can't find anything on metallizing. I'd like a chart, similar to AISC, that shows the slip coeficient on metallizing. They have one for zinc primer, galvanizing, and bare steel. But nothing on metalizing.