Carbon Steel Stair Treads - Can I (Should I) galvanize over Dykem Blue layout fluid? 1

[racookpe1978]

Installing a series of 3/16 thick carbon steel stair runners. On gates and railings, I usually weld up and then wipe them clean with a paint thinner to remove mill scale and oil, then cold spray galvanizing paint on the metal. Then finish with two oats of black oil-based paint as a cover.

For these steps though, many areas are coated already with the blue layout fluid. Is the commercial cold galvanizing paints effective over the layout fluid, or a waste of effort since there is a few micron's between the galvanizing primer and the metal? Or just accept as-is, and apply the top coats as usual? No salt spray, but outdoor exposure.

Commercially, I've seen many items coated with the Dykem Blue in the laydown yards for CT and turbine internals that will go back into the turbines, but need a short-term coating against incidental rusting. Obviously not a permanent coating, but will it foul up the regular paints if left in place?

 

[SJones]

What does the datasheet for the zinc rich paint say regarding surface preparation?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[TugboatEng]

Inorganic zinc paints require a surface free of contaminants to be effective. It's essentially an electrical connection you're making. Otherwise, you're wasting your money with the zinc and any other paint system would suffice.

 

[racookpe1978]

That was the direction of my thoughts: The instructions on the galvanizing prier "seemed to" not require a bare bright surface, but on further reading, that does not seem correct:
"Remove any dirt, oil, grease or contaminants by washing with (Rustoleum) Original Krud Kutter Cleaner Degreaser or suitable cleaner and water. Rinse with fresh water and allow to dry. Remove all paint and loose rust by sanding or wire brush. Lightly sand glossy surfaces. DO NOT PRIME. Do not topcoat with an alkyd finish."
Now, the "DO NOT PRIME" in their capital letters! is certainly emphasized and very clear. "Remove all paint" is also clear. But, if a glossy coat (already painted ?) can be scuffed up sufficient to be acceptable, then don't a few microns of the Dykem (laquor ?) merely need scuffing with a wire brush?

 

[TugboatEng]

There are solvents that remove Dykem. You could just wipe it off.

 

[SJones]

Tugboat gave the correct reason: the galvanic action of the paint (and the adhesion) requires a clean interface with steel. Also, if the Dykem peels, then so does your paint on top of it. The instructions are pretty clear. You might also want to pay attention to the overcoat: the "black, oil based paint" might just be an alkyd.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[Tmoose]

" usually weld up and then wipe them clean with a paint thinner to remove mill scale and oil,"

Good weld prep would be to remove that stuff 1" or so back from the welded joints before welding. Some electrodes handle mill scale and dirt "better" than others.

I'm guessing these are outdoor stairs, so it won't take much foot traffic to wear thru the paint and cold galvanizing and let the rust begin.

https://p1.pxfuel.com/preview/885/971/829/urban-stairs-rusty-outdoor.jpg

 

[racookpe1978]

One (small) advantage, the treads will be pressure-treated wood, but the risers (cantilevered out from the central post) are corrosion-likely. And (obviously) the welds between each riser and central post-and each riser to its upper and lower neighbor.

Yes, I understand the reasoning for the 1 inch clear-ground margin around each weld - that will be done when work can resume.

My appreciation to all. I'll report the results when complete - when exposed after that to what I hope will be only reasonable wear and tear.

 

[berkshire]

One thing to note with Dykem Blue, is that if it applied too close to a weld, it turns brown and is very resistant to solvent removal, requiring wire brushing or abrasive removal. Due to its temporary nature The layout fluid is nor durable and will eventually peel off taking whatever you applied on top with it.
B.E.

You are judged not by what you know, but by what you can do.

 

[racookpe1978]

Hmmmmmn. Things are good to know.