Rust on Front Edge of Hoods

[Countryboy]

The front edge of a hood catches the hardest abrasion from dust, bugs, road sand, etc. This is why it is common for the front edge of hoods to get chipped or start rusting first.

The leading edge of airplane wings (and old wooden props) is often covered with a more resistant material to withstand abrasion.

Boat propellers also can show abrasion marks first on the leading edges.

[Allen Dick]

Good Point. I have foil on the leading edge of the prop on my ultralight.

The thing is, though, that the rust seems to start underneath in the seam. It has gathered sufficient rust to actually pry the fold open. Seems water gathers in there and repeated freezing (expansion) then thawing does the dirty work and rust never sleeps once it gets a start.

Have not really examined the Toyota, though. It fits your description better. I'll have to look. Thanks.

Anybody have an opinion about those electronic gadgets that supposedly prevent rust from advancing?

[peterdbk]

regarding electronics gadgets to stop rust from advancing.

This is off-the-cuff, but I think rust is an electrochemical reaction, like a battery, so one might be able to retard it by keeping the clean metal above some voltage. But ...
"In theory, there is no difference between theory and practice. But, in practice, there is."
(Jan L.A. van de Snepscheut and/or Yogi Berra)

[Allen Dick]

I know that with boats, electrolysis is a problem and can be mitigated by isolating the boats' electrical system properly and by attaching sacrificial anods.

See http://marineinsight.com/marine/underst ... -on-ships/ (The above is not the best article I've seen, but it is handy).

On a car, though, where is the circuit? What is the electrolyte. I've looked online and never found a convincing story or any kind of controlled study. Is this in the same class as "fuel magnetizers" and other such snake oil, or is it real science? I have not been able to find anything except testimonials from people who have no real way of knowing if it works, and who would be biased to thinking it does since they spent $200.

[Countryboy]

I have heard of using sacrificial rods buried in the ground to stop rust on metal barns. That sounds similar to what you are talking about with the boats.

It's possible that you could rig up a sacrificial rod that would be the first to oxidize, rather than your car rusting. I'm not familiar with that though.

Do they use much salt on roads in Canada? Here, winter salt on roads is the biggest cause of rust on vehicles. Once the salt eats down to bare metal, then the rust gets under the paint. It's possible the salt from roads is able to eat down to metal easiest at the seam under the edge of the hood.

[Countryboy]

I worked in machine shops for a few years. Precision measuring tools can be pretty pricey. Something many machinists would do is to put scrap pieces of copper in the drawers of our toolboxes. Folklore was that a piece of copper would tarnish before our tools would rust. I don't know if it was true or not, but many oldtimers had copper in their boxes, so I put copper chunks in my box too. It was cheap insurance if it worked, and I wasn't out much if it didn't. I don't know if it made a difference or not, but I never had problems with micrometers getting rusted up.

[Allen Dick]

Yup. Salt is the culprit. Alberta is not as bad as some places, though because, I think, of the low humidity.

Newer vehicles are much better due to galvanizing and better steel, but there is s still a problem. In the cases I'm seeing, the rust starts where the coating is compromised and corrosion starts.

It seems the leading edge idea might explain the reasons for hoods rusting there. Could also be the action of grit and abrasion. can't recall seeing it on cars, though.

[peterdbk]

In the boat example, the circuit presumably involves the water the boat floats in.
The analogous circuit completion for a car would be either the air (works better when humid) or a film of water on the surface of the car (from dew or rain). Either way, if you have a charged conductor, the charge will congregate at sharp edges or protrusions.

Gotta go to dinner. more thoughts later if I have any.

[peterdbk]

I posed this question to my daughter who has had a couple of years of high school chemistry. She thinks we are on the right track.

So the way I imagine this rust prevention device being constructed is as follows: Create a voltage (maybe) 5 volts below car battery ground and connect this to a conductor that contacts earth ground (pavement) under the car. The rubber tires electrically isolate the car from the pavement. I note that all steel in the car body and surfaces is electrically connected to battery ground which is now 5 volts above earth ground. I am making the assumption that the air within 10 ft of the earth is usually at a voltage very close to earth ground.

I think there is a reasonable chance this will work, although I gain recall the difference between theory and practice.

[Allen Dick]

If that is all the thing is, then howcum it costs hundreds of dollars? Seem there are several brands, too.

I've spent some time on the 'net looking for an explanation or a definite answer and all I've found so far is speculation. I wonder if Consumer Reports or some other reviewing organisation has tested them.

I wonder how they could test them?

[peterdbk]

> I wonder how they could test them?
I would test it on a piece of angle iron resting on an old car tire outside. A second piece of angle iron on a different tire would be the control. There ought to be observable results in a month.

Since this is a beekeeping website, here is a better test.
1) put two old tires flat on the ground, side by side but not touching.
2) put an all-wood single-story beehive on top of each tire. Use waterproof wood top.
3) put a piece of degreased angle iron on top of each hive
4) put rust prevention device inside one hive (to keep it dry) and run 1 wire to earth ground and one
to the angle iron on top.

The rust prevention device as my daughter and I envision it could be prototyped as 4 flashlight batteries in series connected in series to a high-value resistor. Since I just guessed at the polarity of the device, maybe you should have three stations: angle iron +6 volts, angel iron -6 volts, and control. Volts are relative to earth ground. The purpose of the resistor is to avoid draining the batteries or having sparks if something in the environment creates a temporary short (such as a heavy rainstorm).

[Allen Dick]

Makes sense to me. Now, I wonder what is inside the $200+ boxes on the market.

I suppose I should buy one and subject it to some non-destructive testing.

[dtompsett]

All of you have touch on the major root causes of rust on the hood...
-abrasion/stone chips compromising the paint/galvanizing seal (not sure if all cars are galvanized now-adays... but if a stone chips off the paint, likely it'll nick the galvanizing... and then it's only time.)
-seams holding water/salt... freezing water can push apart seams, salt water can find it's way down into all the little nooks and spots that paint and seam sealer don't get.

How can you prevent these sorts of problems?

-Clear 'bra' material... many shops are capable of applying this material (look for tint/paint/body shops). It's a not-so-thin film (2mm thick?) that sticks to the paint. If you've got a good rust-free hood, this is the first defence against stone chips. This can also be applied to rocker panels, fenders, the painted front of side mirrors... the plastic film takes the abuse, not the paint. It's not easily removed though... and eventually it will start to turn yellow due to UV exposure... but the products on the market have improved a lot in the last decade.

-Touch up paint... see a chip, get on it before it starts to rust!

-repaint, but coat with a rocker gaurd material... if this isn't your show car (ie, you just want to prevent the hood from rusting on your 15yo car), clean and prep it, tape off the majority of the hood leaving the first few inches exposed. Spray on a paintable rocker gaurd material (I think there are products meant specifically for hoods to be a little smoother), then paint when ready. The paint might still become chipped due to rocks, but the material underneath will absorb the impact and keep the paint sealed.

-undercoating/spray oil. I used to work at a Krown rust-proofing shop... you know, the place where they drill holes in the body of your car/truck, spray oil all through the frame, then cap the holes with plastic plugs. Best if you have it done annually. Lets just say I'm a believer in this. If you can talk with the guy who's doing your car, be sure to mention areas you'd like specifically addressed, like the seams in the hood and the trunk lid... cause it never hurts to remind them. When I worked at that shop, we had an old guy bring in his winter beater that he had sprayed every fall (helps keep the salt water/moisture out of seams)... he specifically said he didn't want his trunk lid drilled to let us spray inside... keep in mind this car is a 'repeat customer'... lets just say this old winter beater had no rust anywhere on the body except one place... the trunk lid.

Just some things to keep in mind.

[Allen Dick]

Interesting that you mention Krown. I've heard good things, but also that it entirely depends on the franchise -- and the guy on duty -- how good a job you get.

Where was the shop where you worked?

Do you think that it does any good to Krown a vehicle which already has a touch of rust?

[dtompsett]

Where was the shop where you worked?

The shop I worked in was in Peterborough Ontario, back when I was in high school. Dad was taking several of our cars there and convinced the guy to let me work the odd evening/weekend.

Do you think that it does any good to Krown a vehicle which already has a touch of rust?

Definitely yes... while it may not do much to stop the rust (other than getting a coat of oil on it to keep the oxygen out), it will benefit the rest of the vehicle.

I know one truck we had, dad spent a long time with the truck parked on an incline flushing out the frame rails (which were full of dirt/mud) before taking it in to be sprayed... and specifically requested that the guys spend some extra time spraying in the frame rails!