Dealing with these small, black rust dots and lines

Schroeder

Promoted Users
Are these of any concern?I've ran a surface conditioner over the surface. It is a really good panel over all. It's really solid. The backside is good. It isn't pitted. Do I need to blast this our? I'm concerned with warpage if I do that. If that's the answer, what should I do? Use the finest media and lowest pressure possible to get the black to disappear? Is OSPHO the answer?
Will this really be an issue? Thanks in advance.
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They are a concern. Some spots like this can hide after using a wire brush or stripping disk by polishing them. A coat of naval jelly would bring out any hidden spots by turning them black. Use more jelly to lift out the rust, then a spot blaster would clean the small pits using fine media.
 
I think it would be tough to warp anything with this.


Don
 
What you are showing appears to be a pit from the front side as it looks like a depression that the "surface conditioner" has collected in. This will need to be removed by any means necessary as it is still an acid that will be under your paint. Some exposure to the hot sun (think car shows...) and the residue of acid in that pit will activate from the heat and start to outgas from the chemical process. This results in delamination and little tiny circles visible in your paint. I would use a real fine media and low pressure to address the isolated areas needed..


As an FYI, and since your car is in bare metal, circles of a darker grey in your bare metal without a depression in the metal are indicative of a rust pit coming through from the back side.. The following is from the top of a 55 fender that has a stiffener bracket underneath. Tires throw dirt and water and this bracket becomes a trap for them. You can see the pitting from the rear side, and although I used an ice pick to test these there is a small dark circle on the top side there next to the one hole on the right to show what they will look like. My suggestion if you find any dark circles like these is to check the back side, and absent accessibility, use an ice pick to see if it is indeed a pit coming through. Cheaper to fix before the paint goes on. If you don't catch it at this stage the pit will be coming through your new paint within two years..


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Would it just be best to replace the fender? I'm adding a flare, cutting the top surface to gap with the hood perfectly, and deleting the marker light, so there's already metal work being planned. Would I be better off just starting with a set of OER reproduction fenders? Does anyone have experience with them? Do they for ok? Again, since I'm doing some heavy customization anyway I'm not sure how perfect the for has to be.

Classic industries has a sale through the end of the day for Christmas. I'm wondering if they'll have the same or better for new years though too. Seems like last year their new years sale was better than their Christmas sale!!
 
Some reproductions are fairly accurate where others require quite a bit of rework to get gaps and body lines correct and still others are so far off that you may as well find something from a junkyard in AZ. For many of the reproductions I’ve run across I had the owner send them back and either made the part myself or repaired the original. At the end of the day you need to be comfortable with the parts you’re buying or comfortable with your skills to get you to your end goal.

With the modifications you have planned, if much of the defect areas are being cut out, then it plays in your favor in keeping the original stuff that fit. My suggestion with respect to the reproduction parts is to check some forums specific to the vehicle to see if there is feedback on which parts may or may not be accurate.

Lastly, I lightly touched on the subject in my previous response, but I have had past experience with adverse effects in using Ospho. Or rather spraying the car after the owner had applied a generous amount of Ospho on a very pitted area. My first experience with it, his buddy “did this all the time and recommended it” . At the end of the day, Ospho residue left in the bottom of the pits was a collection of acid. When he took the car to shows all that year and it sat in the sun all day, the acid residue was activated and going through its chemical process, which also means gases given off. This results in delamination and every one of those pits showed up in the form of raised circles about 1/8” or less in diameter where the epoxy primer was being pushed away from the metal.

Ever since, I have gravitated toward using media blasting or replacing rust with fresh sheet metal. It’s a lot of work in painting a vehicle and rework stings fresh in your mind despite the passing of time. So if some of my recommendations or repairs seem excessive, it is this past rework that drives my methods. While I have no plans of using Ospho in the future, when others here stress the removal of residue from pits through thorough rinsing, spot blasting, or whatever the method, take heed. Most shortcut products include their own set of pitfalls (pun intended). We as humans are naturally lazy/looking for the easy way to do something. It’s here that the allure of easy work gives us a false sense of security where someone may not clean acid residue as throughly as necessary. Rework/ repainting the entire car is a harsh lesson not forgotten.
 
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They are a concern. Some spots like this can hide after using a wire brush or stripping disk by polishing them. A coat of naval jelly would bring out any hidden spots by turning them black. Use more jelly to lift out the rust, then a spot blaster would clean the small pits using fine media.
Isn't this an acid like OSPHO?
 
Yes, it’s phosphoric acid based, but if you apply it, and wash it off before it dries, it’s safe IMO. Just be sure to clean it like Barry says. Others on here use it with good results. I’ll usually do a quick blast of small pitted spots as well after using naval jelly. But if it’s just surface rust, there’s no need to blast, as long as it’s cleaned and prepped probably. Sure, it’s the lazy way to get rid of rust. But if I apply it, and cover it with plastic to keep it wet, I can work on something else while it’s working for me.
 
I had the same 'zit' issue on sheet metal with the last car I restored, especially the hood and trunk lids. Don posted above about using a small Zendex blaster. I use something like that but it also has different shape hard rubber adapters on the noddle to not only spot blast but also collects the media into a recovery bag without it blowing all over. I see Harbor Freight no longer sells that unit but here is an equilivent on Amazon that can be used in addition to the Zendex unit. https://www.amazon.com/Zendex-Tool-...1640618940&sprefix=spot+blaster,aps,77&sr=8-2
I use 80 grit glass beads and about 40 PSI working pressure at the gun instead of the 80-90 PSI and haven't had issues with metal stretching.

Mike
 
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