Are you using electro-plating or hot dipping?
There are several ways to check thickness, but using an elcometer would not work because of the small section size. You will likely only be able to determine an average thickness of the coating over a large area. This can be done by accurately weighing the specimen before and after coating. You will have to determine the surface area of the mesh also.

I only use electroplating for dry interior spaces, not subject to a corrosive environment... else, HDG is the only way with zinc coating. I have photos of electroplating in a corrosive environment after a month... and looked like no coating at all.

Dik

Dik...I agree. Electroplating is too thin to be of any real use. Not any better than a good paint coating.

@dik


Please share the PICS .

We are doing both electroplating and HDG. In HDG we are facing so many problem in surface finish and post process finishing work is so high . As it is manual,we are spending so many manpower on same thats why we are suggesting our client to purchase electroplated materials.

In grinding there is big loss of coating thickness of HDG materials . Is there any other method to do the finishing with small machines ?

Quote:

so many problem in surface finish and post process finishing

Perhaps some photos of your product before and after dipping and before and after finishing would help us understand why you are having to grind HDG at all.

Mike Halloran
Pembroke Pines, FL, USA

This is before HDG

This is Before HDG

This is after HDG .We are doing filing to remove this zinc lumps at edges and painting with zinc rich paints in the uncoated areas ...

OP:
I'll see if I can locate the original file, else, I'll scan the one I have on my wall.

Dik

When you HDG, there is generally a 'scum' that forms on the surface and this is usually removed prior to extraction from the zinc bath. It does not appear that this has been done. Your HDG does not appear to be 'clean'.

Dik

Some of your photos appear to show "swipe" marks in the coatings, which would suggest that your surface preparation is not particularly clean

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I thought you started asking about coating wire mesh. The pictures show something else entirely.

@hokie66

Ysss. but as i mentioned above we are doing electroplating because of these issues in galvanising.

Right. I see you have issues. But the corrosion protection afforded by galvanising is vastly superior to electroplating.

IR... the 'swipe coatings' look like they were caused by withdrawing the object from a 'dirty' tank.

Ratheesh:
Attached scan... couldn't find the photo.

They said the sag rod was electroplated... doesn't look like this happened, else, the corrosion is extreme.

The channel girts were supposed to have an epoxy zinc rich primer, with a high build epoxy intermediate coat, and a polyurethane top coat... ditto above. The pin prick corrosion centres indicate a poor application of a quality coating system, or maybe a different coating system.

The siding has a CSSBI Barrier coating and seems to be holding up (still).

I refused to sign off on the installation, and, had specifically noted on the shop drawings that the sag rods were to be HDG.

Dik

• http://files.engineering.com/getfile.aspx?folder=8df9c710-1ad3-4395-90e3-a2

Thanks Dik for Sharing the Pic


For Extreme corrosion environments like offshore , Coating system should be Zinc silicate primer + High build epoxy paint 2 coats + Polyeurethene finish paint or to be HDG .

I'll look into the zinc silicate primer. The zinc rich epoxy has worked well in past, but, if there's something better, I'll use it.

Dik

Hello Ratheesh,

I understood your situation.

So, go for chromate treatment for better corrosion resistance after electroplating.

Regards

CocoE

CocoE:

I generally spec, "HDG EXPOSED TO THE ELEMENTS SHALL BE PASSIVATED USING A NON-CHROMATE PROCESS", because of health related issues with Chromate treatment. Passivating the HDG material will not likely resolve the coating issue. It's likely related to the actual 'dipping'.

Dik

Dear Dik,

Could you please read my reply once again?

I am not saying to do chromate treatment to solve the galvanizing defects. My suggestion is to do it on "electroplated" wires, and I hop I am not diverted from the initiator's question. HDG is always best solution than electroplating due to many reasons (no alloy layer, less thickness, less Zn density), I was just trying to help him out to make his product better.

Also, for your information, all chromates are not having health issues, and if you can go through ASTM or ISO electroplating standards you may find it right there.

CocoE

I did... but, would not passivate electrogalvanised material. Only use for this coating is interior non=corrosive environment, IMHO.

Dik

Dear Dik,

Yeah mostly only non corrosive environment due to the factors I stated above, but I have seen electroplated "items" are used even on the exposed (I am not saying it really corrosive) locations where HDG may cause undesirable changes like clogs, lumps or uneven build. Electroplating or mechanical galvanizing (small components) are often used in such occasions where a good surface finish is desirable.

What do you say on that?

CocoE

If the environment is non-corrosive, sure, use electroplating... zinc, chrome, or whatever..

If finish and tolerance is essential, and it is a corrosive environment, then construct it out of material that is non-reactive.

I specifically stipulate that cadmium is not used.

Dik