CC DIY: 2007 Honda Fit – A Rattlecan Rust Repair

I grew up in the salty north where rusty cars were a fact of life.  In my youth anything I could afford would undoubtedly come with some rust.  And having at least some pride in whatever I drove, learning how to deal with that rust became a crucial life skill.

Fast forward about forty years.  Modern cars do not rust nearly as badly as those of the 1960s and 70s.  OK, except for Mazdas, but that is a topic for another day.  Honda in particular has made amazing strides in this area.  Through the first half of the 1980s Hondas were rusters.  But then this changed and we rarely see really rusty old Hondas.

With one exception.

Hondas of the last generation or two have developed a tendency to turn brown in a little corner of the rear quarter panel where it meets the plastic bumper right over the rear wheel.

My Honda Fit was the first new car I had bought in many years.  It is now right at about twelve years old (having taken possession of it in November of 2006).  Over the last couple of years the “Honda rust spot” has been developing.  In my mind I knew what I needed to do.  But in another part of my mind this was still my new car and the idea of using sandpaper and a spray can on it was something I just could not bring myself to do.  By this summer, however, the problem had become unavoidable.

Close up of the mounting point for the forward edge of the bumper cover (driver’s side). Note the gap between the dark plastic bumper cover support and the quarter panel, caused by the nylon nut. Muck and crud collects between the cover support and the metal quarter panel in the area of the circle. This photo was taken after the repair.


First, why do these rust here?  I now know.  Where the wheel opening meets the bumper cover there are several plastic parts that come together.  A nylon nut pops into a square hole in the steel quarter panel lip.  A black plastic piece that holds the bumper cover in place (a bumper side support) terminates with a half-hole over the nylon nut.  The bumper cover itself has a hole there and a little screw goes through the hole in the bumper cover, then through the plastic support and into the nylon nut in the steel quarter panel.

Underside of the passenger side quarter panel after removal of the bumper cover support and the nylon nut. This was the good looking side.


There is perhaps 1/16th of an inch of space between the steel panel and the black plastic side support which invites a layer of muck to collect.  The moisture trapped there gets under the paint around the nylon nut and then begins working its way out in every direction under the paint.  It eventually eats through the outer sheet metal surface and continues inward until something is done.  And so I began.

Driver’s side before the repair.


The plan was to attack both sides.  The drivers side was the worst.

Passenger side before the repair, and before removal of the bumper cover support piece, which I had to pull out of the way in order to get a good look at the situation.


The passenger side was in a much earlier stage.  Depending on my level of impatience during the process I took photos at various stages of both sides.

Driver’s side. My fingers are near the rear tire and the taillight is at the far right edge. This piece was accessible by bending the flexible bumper cover back out of the way far enough to expose the Phillips screw that secures the back of the piece. There is a plastic access panel on each side of the cargo area which provided access to the back sides of the fasteners.


It was soon apparent that I would need to remove the plastic bumper cover support to get decent access to the rusty metal.  There is a Phillips head screw that attaches it to the body at the rear of the piece and a plastic tab that pops into a slot which secures the middle.  I ended up cracking one of them while I learned the removal technique, but some J B Weld fixed it right up.

The nylon nut that presses into the quarter panel and the Phillips screw that attaches the bumper cover to the quarter panel, after both were removed and cleaned up a bit.


The front, of course, released when I removed the screw that attaches the leading edge of the bumper cover to the quarter panel right behind the wheel opening.

First: Grind.  Years ago I discovered these plastic abrasive sponge pads from The Eastwood Company.  They are abrasive enough to remove paint and surface rust but soft enough that they do not take a lot of metal with them.


Passenger side after some initial grinding with the abrasive wheel.


The passenger side shows how this job would have gone had I gotten a start on this a couple of years earlier.  Getting most of the paint/rust off of the lower quarter lip was a start, then I went as far up the outside of the quarter panel as was necessary on each side.

Driver’s side. The ugly truth. Perforation began with the exterior panel. There is some rust on the interior backing metal but it still seemed reasonably solid with no perforation.


The drivers side proves my causation theory.  The outer layer of steel was eaten away but the backing was intact.  There was no rust-through evident from the underside of the car.

The Oxy-Solv clearly did something. Compared with the photo above, the lower edge of the rust showed significant color change. Also the shiny metal took on a satin look. I was not satisfied with progress on the interior metal.


Second: Treat.  I still had an old product called Oxy-Solv that I had bought from Eastwood.  It chemically treats the rust and converts it to a zinc oxide (according to Eastwood anyway – I am no chemist).  It worked – some.  Whether it was the age of the stuff (over 20 years) or my impatience, it was not doing its thing fast enough.

Very poor blurry picture of the driver’s side after the rust dissolver had cured and turned black.


I went to Plan B – a Rust-Oleum product called Rust Reformer.  The instructions say paint it on and let it sit for 3 days, then fill or paint over it.  Will it work?  We shall see.  If When I have to do this again in a few years maybe I will have some more experience with these rust-stopping compounds by then.  If there is a weak link to this repair it is right here.

Driver’s side after rough spreading of Bondo Plastic Metal.


Third:  Fill.  The passenger side would need nothing beyond prime and paint.  The drivers side, however, was too far gone for that.  Some Bondo Metal Putty was the filler of choice.  I have not used this particular product before but have it on the authority of an old body man that metal putty tends to last longer than traditional plastic filler.  I spread some over the low spot then came back to sand it down smooth after it had dried.

Driver’s side after partial sanding of filler. There are some difficult contours to work with in this particular spot.


This is where some of my impatience came into play.  This was being done in mid October so temperature was becoming a limiting factor.  The number of good days (warm + dry) for painting was dwindling fast, so I got in a hurry.  With more patience and more time my putty sanding would have resulted in a perfectly smooth surface that matched the original.  I did not quite get there, becoming belatedly satisfied with a bit of a high spot over the main place of the repair and a couple of little depressions elsewhere that could have been fixed with another small putty application.  But sometimes good enough has to be good enough.

Interlude: Other Stuff.  While waiting on rust treatment and putty to dry/cure I turned my attention to some of the lower plastic pieces that have gotten badly scraped and scuffed over the years.  Under the white paint is black plastic, so the scrapes and gouges stood out like a sore thumb.  And generated multiple reminders at home that Mrs. JPC had certainly not made any of those marks, so they must have all been me.  Mask, sand, prime and spray.  My paint technique will be explained below, but this part came out pretty well except for a slight difference in the shades of white between old and new.

Fourth: Prime and Paint.  Dupli-Color spray cans and I have a long, long relationship.  I have had great results with it, and I have had some that have been less great.  There are two variables – color match and surface preparation.  I can control only one of these.

After a light sanding with 400 grit paper some primer went on.  One of the best tips I ever got was to NEVER mask off the  actual repair area.  I masked off areas farther out from the repair to protect from overspray, but paint application was controlled with a piece of cardboard held in my non-spraying hand.  With the cardboard held about an inch from the surface being painted, spray normally.  You get a nice, soft edge that will not leave you with a “masking tape ridge” you have to deal with (or look at).

One other trick – if you do spray up to the masking tape edge (as I did with the plastic trim pieces) do not press the entire width of the tape against the surface.  Instead, press half of the strip to the surface and then fold the other half of the tape out away from the panel.  This is another way to soften the edge of the new paint so that it will be easier to blend.

Driver’s side after priming.


Each step (primer, color, clear) will go just a little farther out than the last step so the area of between-coat sanding will get a little larger each time.  Although I normally try to extend my new paint to a character line or panel edge I decided against that here.  Because I was short on time I did not want to paint that much, which would have involved going to a ridge midway up the quarter panel and down the dogleg ahead of the rear wheel. Also I have no experience in spraying a clearcoat over single stage paint and decided that the smallest area possible would be prudent.  If I experience some kind of failure the problem area will be smaller.

Passenger side after color spray.


After the primer dried I did some light sanding with 600 grit paper.  Now for the moment of truth.  Dupli-Color Perfect Match spray is a two stage lacquer product.  My car was originally finished with a single stage enamel.  Going from one kind of paint to another is sometimes a problem, but in my experience new lacquer over old enamel will work.  (I recall the opposite being a really bad idea).  A single stage spray would have been perfect for me, but those have become largely extinct for we driveway-painters.

One problem was the color coat itself.  It was a frustrating mix of two seemingly irreconcilable traits.  It did not cover all that well well yet with that one last spray pass for a little better coverage would cause it to begin running.  Given the threatening weather (and after some bad words) I pressed on.  A little between-coat sanding took care of the small runs I got in the paint.

The result. Driver’s side (left) and passenger side (right).


After two or three applications (with light sanding in between each of them) we got to that place – good enough for a twelve year old car in late October.  The final step was the clear coat.  A light 600 grit sanding on the color (and just a bit out from the new paint) and I sprayed clear on an area slightly larger than my repair.  And . . . done.

Close up of the Driver’s side, proving the rule that paint will not cover substandard body work.


Am I completely satisfied?  No.  I know that if I had started this earlier in the fall I could have taken my time and gotten a better result.  I know that I have the skill to make this come out really right, but it was going to take time that I did not allow myself.  I am also honest enough to know that in this part of the country rust on a daily driver always comes back, so this will not be my last opportunity if I choose to keep the car.

Before (March 2018) and after (October 2018).


But on the other hand, white is a very forgiving color in that surface imperfections are not easy to see.

The Author’s Honda Fit Summer of 2007 (top) and November 2018 (bottom)


If you get up close you can see that the repair is not perfect but from roughly 97% of the angles and distances that matter I have a Honda Fit that looks not a whole lot worse than it did when it was just a baby.   The car has a lot of life left and I like it, so it was worth the time and effort.  The opening photo shows the finished product.  I am happy.

Further Reading:

CC Long Term – Ten Years Of Keeping Fit

CC Update – Lacking Clarity