Had this custom bookshelf built ~8 years ago. It was sprayed with a water-based stain. This year, spots started to show, almost looks like the stain dried out. Any ideas why this happened now? is. there a name for this type of discoloration? is the only option to fix it to re-spray it?
Since you can see the stripes on the left, a pattern on the lower right above the outlet and lighter areas on those seams on the top middle section, my guess would be that there were adhesion issues... maybe some of it due to the way it those joints were filled (or maybe what type of filler was used) and sanded or the way some of it was prepped. This can sometimes happen when spraying finishes that dry quickly. Yes, it probably needs to be refinished.
And I would assume you have a clear finish of some type over the top of your stain. It's possible the problem is only with that clear finish... but it's hard to say from just a photo.
So I learned something new...
We have a couple bollards at our congregation that were new about 4 yrs ago, and someone painted them safety yellow using what I assume was a DTM (direct to metal) oil based paint. But within about 1 year the paint was all peeling off in big chunks. It didn't take too much effort to scrape all the old paint off, the adhesion of any remaining paint was poor. This was due to the oily, slick surface (passivator) on the galvanizing. And turns out all alkyd oil based paints will eventually react with the zinc on the surface and peel.
The passivator must be removed by [color=#333333]SSPC-SP7 (meaning, a certain level of brush off-blast cleaning).
But apparently you can also successfully paint galvanized that has sufficiently weathered. The test is to see if you can chemically etch the galvanized with a solution of Copper Sulfate, salt and water. If it does NOT turn greenish black, the passivator remains on the surface and it must be removed by blasting. (Or weathering)
If it weathers TOO much, the galvanized will get a white oxide which must also be removed to successfully paint the surface.
So I mixed up about 70 mL of Copper Sulfate, 70 mL of salt and dissolved it in 700 mL of hot water. Sprayed it on the bollards with a spray bottle (gloves and goggles) and within a few seconds it was turning greenish black. And the whole surface seemed to take the etch evenly. This was no doubt due to about 6 months of weathering since we stripped the old paint.
So the next step is to prime and paint, but this time I notice that Sherwin Williams recommends only water-based/ latex paints and primers. So we'll see how that holds up this time.
I was wondering [utag=134565]marksr[/utag], what did you find to work well on new galvanized metal that you painted?[/color]Read More
I'm finished with the mud work and am into the sanding. Being a layperson I've never quite gotten the hack of doing drywall. Too much mud! Way too much. I've completed a big DIY project in the past and when I'm finished with the sanding and painting it turns out pretty good for a novice. But, like I said---too much sanding. My question is: I'll be putting knockdown on the walls, so I would like to know if I might be too meticulous in my sanding. A friend said, "When you put the knockdown on you'll wish you had put it on a lot sooner rather than being so worried about your sanding." So, will knockdown hide a lot of flaws? In the job referred to above I didn't do knockdown and just painted. I know paint will reveal every mistake but I had sanded to the point that there were very few spots that I had to go over with the mud.Read More
05-30-23, 03:25 PM
