First. If you attempt this, you should either not really care too much about the car's paint job, or plan on getting a paint job EVENTUALLY in the life of this car, or just don't care about that spots looks. This instructable was made to quickly get rid of rust, mostly surface rust, and protect it from further rusting. without using actual more expensive car rust products. Women and cashiers married or not check you out at hardware stores, you should know that! Do your car rust repair stealth!
Note, that professional rust repair and home rust repair is vastly different. A professional will cut the rust out completely, and then weld a new comparable metal to it, bondo it and paint. This is kinda unnecessary until you get rust in the same spot repeatedly IMO. It can also create more rust because you can't sometimes protect the back of the weld on the new metal!
So this is my rust. It looks kinda bad, but it really wasn't. The rust went a LITTLE under the paint, which you have to look out for. You 100% need to get rid of ALL the rust or it will be back at some point. Don't let rust cans at the hardware store fool you. NEVER just cover rust. You will never ever cover it 100% due to it not being flat, and it's just a HUGE no no.
What you need
Sand block about 4 inches long
60 grit sand paper
140 grit sand paper
400 grit (additional metal smoothness, and for extra paint layers, this is kinda optional but should REALLY be done)
(Armor Coat) Metal outdoor rust paint from the regular paint section in your color (car rust paint ~$12, weird instructions, generic metal rust paint, $4 with tax!)
(Armor Coat) Metal/wood outdoor primer (kinda optional but recommended for extra protection)
Step 1: Remove Wheel Well Protection
At this stage, you might want to look at any rust on the inside under where the plastic protection was. Mine has a little spot there too, again its just surface rust RIGHT NOW. An under car liner can solve these issues as long as you remove the rust like explained here.
First picture is with the protector on the wheel well, with one of the screws popped out enough to wiggle remove. Then I have two pictures showing the actual "holder" with the "screw" in and with it out.
Step 2: First Look at Rust and How to Remove
Rust will enter at one spot that has no protection, and slowly spread through the whole car. It will be under the paint to a varying degree depending on when you caught the rust. Sand the paint (60 grit) until you find a small area around the rust not affected.
Here, you use around 60 grit sand paper with a sanding block. You just need something coarse that will "easily" remove paint and rust. I used regular wood grade 60 grit sand paper just fine. Don't put too much pressure, you will need to remove all the hard scratches in the metal later. This is where scrubbing tables or dishes comes in handy! Or wood sanding experience.
MINI SANDING TUTORIAL
A SANDING BLOCK IS 100% IMPORTANT. The block provides an equal pressure when applied to a surface. Your fingers are cylindrical and will not provide a good sanding result. Hand sanding (no block) on metal (or big pieces of wood even) will make many small dips and just plain uneven surfaces in anything you sand.
Always sand in a circular motion as if you're wiping a window or table, and don't put too much pressure on it. Start with a little pressure and add to your comfort. The idea is to remove paint layers and rust. Paint is indeed hard to remove! This should take you time to do! Don't add more pressure!
You don't need a two hand dedicated car body sander for this rust, just a regular about 3 inch block hand sander. You should have one of these anyway for anything you do.
Sanding a car is a bit different. The idea is to get the whole area in one stroke. But like here, you just can't do it. I had rust on the bottom a wee bit too, so I had to break it up, the vertical section and the horizontal bottom section.
Step 3: Removing the Hard Lines in the Metal
Now you need to know basic paint feathering. It's easy but I must describe in a little detail.
Paint comes in various layers. From factory, they seal the metal with a clear sealer. This layer is kinda hard to see, but if you're lucky, you will notice a clear layer that is different from the actual clean metal.
Then there is the primer layer. Primer acts like a bondo for the metal. Bondo repairs imperfections in metal that can't be other wise repaired. Primer does this on a WAY smaller scale. It also gives you a surface to lightly scuff up with the next set of sandpaper we will be using. The scuffing helps the paint adhere to the surface. But we are using spray can paint and this doesn't necessarily apply to us. Primer can be a few different colours, but usually it is white.
Then they paint the primer, and then add a clear coat sealer.
Feathering paint means that you reveal each layer slightly around the bare metal. This makes the painting process easier and makes the end result more flush with a lot less touch ups. You don't have to touch up at all, or feather at all if its a cheap car, but this helps GREATLY if you care about the look.
Step 4: Next Grit Paper
Up your grit to about 140 give or take on what you can find. This like I said is to remove harsh dips out of the metal due to either pitting from the rust or harsh lines from the 60 grit. It also gives the paint a slightly rough but not deep surface to adhere to better. This is really where the sanding in circles comes into play!
So do this until you're satisfied with the result. Perfect world, it'll look like unrusted perfect metal with light swirls that aren't rough at all.
OPTIONALLY BUT PREFERRED you should go to about a 400 grit wet/dry paper after the 140 and do exactly the same thing, except now you're making even smoother metal and the paint will have even better adherence. I chose to do this.
You will need the 400 grit anyway for additional paint layers.
I taped the area to be painted, made sure it was flush, then took newspaper, taped the edges of it with hangover, and taped it to the tape. Then I taped all that down again. I had no overspray onto the car at all this way, but I have done a few spray paint jobs, just not on cars.
Take the time to inspect the car around the area, find places you might not think about covering and cover them. For me, I was going to spray, then realized the whole back of the section I was painting wasn't covered at all! I inspected the back of where I was painting, found zero rust, covered it with newspaper and then continued.
Please do not paint yet! Continue reading next page!
I admit I made a "mistake" here. As you see, this picture is painted. I did not use primer at all on this. I have since bought the primer. It says on the primer, that it hides imperfections in metal and wood, and seals (only) wood. It says nothing about sealing metal at all, and the can of rust paint I used said nothing about using a primer, but said it seals metal.
So its optional I guess. In a car situation, I suggest you use primer, and about 2 layers, preferably 3 for protection. It's another layer, and here, rocks are going to hit that area anyway, so you might as well do it.
In the test spraying you should get your spray position down pat and your spray technique. Basically you want full sweeps back and forth moving down as needed in the "sweet spot distance". Do not move your actual hand when spraying. Point it proper, then move your whole arm back and forth. Never ever move just your hand! This goes for spray gun spraying too!
Right now before you paint, you're trying to learn the ideal distance from the can nozzle to the paint surface. You will notice too close, and you get too much paint on one area and a lot of dripping. Too far away, you get too much coverage area, but not a lot of actual coverage from paint. I think the sweet spot is about 3 to 4 inches away.
Practice on your cardboard until you are confident in your spray abilities. Metal will be different, and one spray on metal isn't just one layer. You might have to spray it a few times until the metal looks covered. One spray isn't "one layer" on a spray can.
BEFORE you paint, make sure you use a lint free cloth and remove ALL DUST AND DIRT AND RUST! I used rubbing alcohol and a lint free cloth.
OK, so this is optional. You used that 400 grit to fix the imperfections of the 140 grit that fixed the imperfections of the 60.
Here is why you really need 400 grit. Additional layers of paint. If you used primer you will NEED to lightly scuff the primer to paint it or add more primer. Again so the paint adheres to the primer better. If you didn't primer, or want to add another paint layer, you should lightly scuff the painted area once it has dried and then proceed to paint it again. The first layer will have needed more paint than the second layer just because of how the spray paint acts on the metal compared to the painted surface.
The painted surface is ready to be layered again when the gloss of the paint is 100% gone but the paint its self is still there. But don't worry if you hit metal, there is a protection layer on the metal from the paint, although it is different from a real car paint job protection layer, it is ok to just paint over it again.
Step 7: Finished Product
To insert the black wheel well protectors, you need to remove the middle "screw", they just pop out with wee bit of force, insert the circular section in, and then pop the "screw" in the middle all the way down until it is flush. The screw, if it doesn't sit flat may require some slight placement twisting.