Petrol neck filler

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961tat
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Petrol neck filler

#1 Post by 961tat » Tue Sep 17, 2019 11:00 pm

In the picture below and on many a petrol filler neck I have resurrected the early ones are far better plated and last longer which is I think very bizarre .

The top one in the picture is a 2005 45 And the bottom one 1997 400 .

https://ibb.co/Hq1kdZv

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Johnny 216GSi
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Re: Petrol neck filler

#2 Post by Johnny 216GSi » Tue Sep 17, 2019 11:33 pm

On my 93K and on the neck from a 92K I replaced it with, they both had a yellow passivate finish much like the one you have your bolts finished in. My car had about 108K on it at the time, and the donor car about 86K. The donor neck was in much better condition than mine however - a lot more of the passivate still left on and only a bit of surface rust. So maybe even as far back as 1992 there was some sort of drop in quality. For what it's worth, I think they should have gone full hot-dip galvanised finish on the filler pipe, or painted it to the same standard as the rest of the car. I had mine sprayed with Epoxy Mastic 1-2-1 in silver, but it's only been on the car for about 21 months so I can't comment on whether it fixes corrosion for good. It should do, if the claims for the product are anything to go by.
Rover 216GSi K reg. Flame Red over Tempest Grey

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961tat
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Location: Lancaster

Re: Petrol neck filler

#3 Post by 961tat » Tue Sep 17, 2019 11:49 pm

Interesting I was think of getting one galvanised , at the moment I acid clean as per picture this eats the rust then use etch or epoxy paint .

Before
https://ibb.co/9wYvGg8

After before paint

https://ibb.co/1d3wjSS

As you can see the rust is eaten and unlike blasting you get all the rust out .

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Johnny 216GSi
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Re: Petrol neck filler

#4 Post by Johnny 216GSi » Wed Sep 18, 2019 12:04 am

Back when I was doing all my underside parts, my rust-proofing method of choice was to wire-wheel or abrade the surface rust off to shiny metal, then spray Dinitrol RC900 rust converting primer which is incredibly active and starts to turn blue/black almost immediately. So I wasn't getting all the rust off - the surface was micro-pitted with rust and the Dinitrol finds that and binds with it. It's a chelating molecular bond - but this is the standard Tannic acid reaction you get with most rust converters - it's just that it's mixed in with an air-drying 1K epoxy primer so it sticks pretty well and seals everything. I didn't know about chemical rust removal at the time, although I'd tried some products that were pretty useless. I've used Bilt Hamber Deox in gel form since then, and this does work pretty well - though I'm guessing it's just phosphoric acid at about 45-50% concentration and mixed with something that gives it a wallpaper-paste consistency so it clings to metalwork and you don't have to do immersion. That's a bit more like your approach these days and if I knew then what I know now, I'd have been chemically de-rusting rather than wire-wheeling everything. Interestingly though - if you use Deox gel and the metal ends up bright and shiny and you tell yourself there can't be any rust on it, if you prep it with acetone (clean/degrease) and spray RC900 on it, it still finds a little bit of rust and starts to turn black - but only a little bit.
Rover 216GSi K reg. Flame Red over Tempest Grey

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crepello
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Re: Petrol neck filler

#5 Post by crepello » Wed Sep 18, 2019 2:37 pm

I find the Bilt-Hamber Deox powder pretty effective. As you dissolve it in water to make a bath, obviously there's a limit to the size of parts which can be treated.
Having said that, I recall making a bath in a discarded plastic ice-cream container, and stood the feet of my subframe in it, in turn, as that was where the tricky rust was.

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