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ChantryOntario 09-20-2013 09:32 AM

A few questions about galvanized metal primer...
Good morning all from Ottawa where it was about 45 F. this morning and its gonna be about 76 this afternoon.....

Ahem... anyway, I have these galvanized gate posts at work that I'm taking down to metal to get rid of the previous(flaking off in sheets) paint job. They will be cleaned with degreaser/rinsed off and then I've been told that vinegar is really good for "etching" pre-primer.... is vinegar effective at all in anybody's experience?

Second thing is, I plan on using rustoleum/tremclad white galvanized primer, I haven't heard anything bad about it, but I've heard that painting galvanized is tricky so I'd appreciate any comments on experience with tremclad in the past.

Lastly, can I use a galvanized primer on bare non-galvanized steel? There will be a few non-galvanized components of the gate to paint after this,and I'd like to use it if possible.

Thanks everybody for any input.

Jmayspaint 09-20-2013 10:09 AM

Yes vinegar will etch regular galvanized metal and allow it to accept a coating. I see a lot of paint failures on galvanized for lack of this step. Like you said, it will literally fall off in sheets..

However, etching with vinegar will only work on regular galvanized. Some galvanized is 'passivated' this is an additional treatment that some types of galvanized metal get. If it is passivated, just etching with vinegar will not work. Media blasting or high pressure water jetting is required to prepare the surface for a coating.

A simple test can be preformed to determine if the metal is passivated. When copper sulfate mixed with water is applied to regular galvanized it will cause a black film to form on the surface. This black film indicates that you are dealing with standard galvanized that can be coated after a vinegar wash. If the metal does not turn black when copper sulfate is applied, it has been passivated and will require more extreme prep to be able to accept a coating. Copper sulfate can be purchased at farm stores as its commonly used in agriculture. You can also possibly get some from Sherwin Williams as they often have it on hand to test for passivation.

A SW, or other knowledgable paint rep could help you with this.

ChantryOntario 09-21-2013 09:20 AM

Thanks a lot for the info. Just goes to show there are a lot of old tricks out there that don't cost a fortune... Now how about those other issues... anyone??

cdaniels 09-21-2013 07:19 PM

1 Attachment(s)
Galvanized metal primers are only for use on galvanized meta and aluminum (at least the ones I've used).You can check the pds for your particular primer but for un-galvanized steel you will most likely need a regular metal primer like this.

mustangmike3789 09-22-2013 06:08 PM

we use copper sulphate to detect mill scale on steel when abrassive blasting. we use a 5 to 10% solution with the same type of testing. the steel will turn orange and mill scale will not be affected. you can get copper sulphate at any store that sells sewer pipe drain cleaner for killing tree roots.

ChantryOntario 09-23-2013 07:29 AM

Thanks again for the info guys. Painting to commence once I clean/pickle the posts and I'll update later.

no drain blues 10-31-2013 03:14 PM

What kind of results did you get?

Did you end up using the rustoleum white primer?

I am having a hard time getting paint to stick to some galvanized. Using SW metal primer (for galvanized) coming off in sheets. As well as rustoleum spray primer for rusty metal (recommended by my metal supplier), it's chipping in places. I etched with vinegar.

Any thoughts on epoxy primer? Would this get any better adhesion?

ChantryOntario 11-01-2013 06:52 AM

I noticed the other day where a chain rubs up against one of the posts that the paint is cut through by the chain. I was able to peel paint away from the cut quite easily, primer included. I had wire brushed,washed, rinsed, pickled, and rinsed again and used tremclad white galvanized primer. Its holding on but not too strong at all.
The finish looks good, and theres no bubbles or anything but it's just not stuck on that well.:furious:

ChantryOntario 11-01-2013 06:54 AM

I will see if I can get copper sulphate to check the area on the post where the chain took the paint off.... any ideas welcome.

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