Fixing rough door scratch?

Question

How should I go about fixing this rough door scratch? Is sanding required? If so what sand paper should I use. What other materials would be needed? I'm new to car repairs but am willing to use any method suggested carefully.

I believe this part is plastic, it's near the bottom of the car door and the car is a Honda Civic 2009 40th anniversary edition.

Edit: Looks like it's not plastic. I'm horrible with materials but as noted by comment looks like rust so must be steel

Note: If I were to go over it with paint, it would still be rough; looking to smoothen out the roughness.

Scratch pic:

Answer 1

It's rusty already so this isn't easy task and you should consider if you are ready to do this by yourself. Might be easier to disassemble the doors and take them to the paintshop. This might cost you a bit, but you'll be sure it's done properly.

But, if you are ready...

There is a proper way of doing this and a cheap one.

Preparation

You'll need some paint. Go to the paintshop so they can acquire exact color of your car. Alternatively you might just buy the proper one using color code of your car manufacturer. I don't know Honda, you'll have to investigate. Keep in mind that there is always a slight difference between cars, so the first option is better.

Proper way

Disassemble doors (so you're left with red-painted element only), sand it properly to the bare metal. Degrease with acetone or any special degreasing fluid, paint with the primer. Let it dry. Then paint them using paint sprayer. Let it dry. Then paint again with the clear coat. Let it dry. Assemble the doors and you are done.

Cheap way

Secure the silver element with paper tape so it won't be painted by accident. Using sand paper (and probably grinder, as it would be easier), get rid of the rust just in this place. Start with rough like P100, then P400, finish with P800. You have to go down to the bare metal. Don't leavy any rust spots (black points) as the rust will develop from them after time. Degrease with acetone. Next, you'll need to put primer. You might use some kind of active one, that dissolves the rust. They work good, but don't expect any magic here. You have to get rid of the corrosion mechanically first. After it's dry, you can lightly treat if with sandpaper to smooth the surface. Then, spray the paint. Do NOT use the brush! It would look very bad. When it dries, put the clear coat and wait until it's dry. Polish it to get even surface.

Answer 2

If It's Plastic

The most professional way to fix it is to replace the trim piece. I can't say for sure that it's not a protective trim piece. I know they are often sold as an option on cars, but I don't know if it was for yours. If you can provide the exact year model (DX, EX, LX, Si etc.) that will narrow things down. Also, asking a body shop, they will tell you exactly what they'd do.

That said, I believe that it looks like plastic. In the image, the far left gouge, looks kind of deep and torn. It also has a black or purplish color (at least on my phone). If it were steel, it wouldn't tear like that, there would be a lot of bending. Even on a car that a friend had which got hooked by a forklift, it was torn, but also bent. This has no visible bending or denting, just these gouges. Also, steel rust is brown to red (depending on iron content). Not purple or black.