2005 W211 rust!!!

[Kev555]

Highly recommend Dinitrol ML for nooks and crannies like chassis legs etc as its got great creep and doesn't seem to dry out from the last time I looked under my Mustang 5 months after application. I did put a coat of Lanoguard over it a week later so possibly its keeping the Dinitrol from hardening. Recommend Lanoguard for arches and easy to reach bits that take most of the salt punishment as its very easy to top up from time to time after a quick wash dry to application areas. Lanoguard is also very water repellent and excellent at neutralising rust.

 

[Craiglxviii]

Highly recommend Dinitrol ML for nooks and crannies like chassis legs etc as its got great creep and doesn't seem to dry out from the last time I looked under my Mustang 5 months after application. I did put a coat of Lanoguard over it a week later so possibly its keeping the Dinitrol from hardening. Recommend Lanoguard for arches and easy to reach bits that take most of the salt punishment as its very easy to top up from time to time after a quick wash dry to application areas. Lanoguard is also very water repellent and excellent at neutralising rust.

I used Dinitrol ML for 7 years on my 215. Worked very well indeed. It does harden over a few weeks, but to a “sticky paint” like state rather than thin liquid. Very persistent.

 

[00slk]

I am very pleased that the Money Pit doesn't have any rust, but it does have plenty of dents

 

[peterws1957]

It still looks solid? I would grind back to clean metal using a dremel and repaint the usual way.

If you can’t get it back to clean metal I find POR15 works really well provided it’s been prepped properly with the metal ready etc.

I did the POR15 ‘bodge’ on my dad W211 years ago and it’s holding up fine. Lives on the cost too so it’s well tested. If it’s just the inner lip, a touch up stick over the top results in an unnoticeable job.

Key is to nip it in the bud early

I'm also a fan of POR15. Panels I did 15 years ago are still rust free. As you say it's all down the preparation which is time consuming, and I always remove rust before application. I still maintain that it is possible to remove rust permanently, all down to the amount of time you want to spend on it.

 

[charlysays]

Done my W220 arches last year. body shop ordered new repair panels. cut out old metal and in with the new.
I had them painted 5 years ago - the rust will just return unless the rust it cut out. Its like a cancer - sad analogy.

That's not the case- you just have to use the right coating and achieve the specified prep levels.
I've had permanent cures using deox gel which completely removes every trace of corrosion even from badly pitted steel like Mercs usually suffer from.

For example jotamastic 90 aluminium (an industrial grade epoxy mastic) only calls for ST2 minimum , ideally ST3 prep which is just thorough power tool cleaning and keying. If you google examples you'll see st2 is a faint metallic sheen with removal of all loose rust and damaged previous coatings, ST3 still has rust pitted areas but is much brighter. These coatings will last 15 years in the sea with the aforementioned prep.

Most other paints, e.g 1k zinc primers need much more thorough prep such as repeated use of deox gel until all traces of corrosion are gone.

I just recently moved over to epoxy primers/ mastics on my W202 but one of the wings I'm currently using was off my old car. 10 years ago it was badly pitted and pinholed in places. I did a thorough job of derusting it using deox gel, painted with electrox primer then aerosol stone chip on the lip, then aerosol paints and it's still perfect 10 years later and is now a different colour on my current W202.

So in short, permanent fixes of even thick surface rust are very possible, they just take dilligence and the right products.

 

[charlysays]

I'm also a fan of POR15. Panels I did 15 years ago are still rust free. As you say it's all down the preparation which is time consuming, and I always remove rust before application. I still maintain that it is possible to remove rust permanently, all down to the amount of time you want to spend on it.

If you like POR15 you should try an epoxy primer or mastic. Having used both, the epoxies are much more forgiving, have better adhesion, compatibility with basically all pre existing metal coatings (apart from greasy ones ofcourse), have anodic materials like zinc or aluminium added for additional protection and are more easily overcoated and easier to apply... they're also far cheaper than POR15 and have a long shelf life even once opened!
Lechler 29107 fast is great for outer panels and jotamastic 90A winter grade is great for wheel arches and underbody areas even if just two coats and no further coatings. They're also surface tolerant meaning you can apply them on partially de-rusted pitted metal (most mercs have lots of this) and the coating life won't be affected (15 year lifespan for jotamastic even in the sea).

 

[peterws1957]

That's not the case- you just have to use the right coating and achieve the specified prep levels.
I've had permanent cures using deox gel which completely removes every trace of corrosion even from badly pitted steel like Mercs usually suffer from.

For example jotamastic 90 aluminium (an industrial grade epoxy mastic) only calls for ST2 minimum , ideally ST3 prep which is just thorough power tool cleaning and keying. If you google examples you'll see st2 is a faint metallic sheen with removal of all loose rust and damaged previous coatings, ST3 still has rust pitted areas but is much brighter. These coatings will last 15 years in the sea with the aforementioned prep.

Most other paints, e.g 1k zinc primers need much more thorough prep such as repeated use of deox gel until all traces of corrosion are gone.

I just recently moved over to epoxy primers/ mastics on my W202 but one of the wings I'm currently using was off my old car. 10 years ago it was badly pitted and pinholed in places. I did a thorough job of derusting it using deox gel, painted with electrox primer then aerosol stone chip on the lip, then aerosol paints and it's still perfect 10 years later and is now a different colour on my current W202.

So in short, permanent fixes of even thick surface rust are very possible, they just take dilligence and the right products.

I bought deox gel a while ago, but have yet to get to grips with it and clearly not using it correctly. Watched some videos on its use recently, in particular the one where rust was completely removed from a very rusty early Pontiac roof. Am I right in saying that you apply it, then cover the area with cling film to prevent drying out, leave it for 24 hours, and then scrub off with water? I presume that if you don't cover the area, the stuff dries out and doesn't work well.

 

[charlysays]

I bought deox gel a while ago, but have yet to get to grips with it and clearly not using it correctly. Watched some videos on its use recently, in particular the one where rust was completely removed from a very rusty early Pontiac roof. Am I right in saying that you apply it, then cover the area with cling film to prevent drying out, leave it for 24 hours, and then scrub off with water? I presume that if you don't cover the area, the stuff dries out and doesn't work well.

Pretty much yes.
Skim off the rust so you have a pitted but otherwise shiny surface.
I find you can get more corrosion out of the craters with a freshly sharpened needle scaler used at an angle to the surface plus low rpm straight bristle wire wheels (I use a cheap right angle air drill).
Apply the deox gel , wait an hour or so to skin off, apply again until you build up a few millimeters thickness then apply cling film. Leave for about 2-3 days, peel back and inspect. At this point I add more fresh deox if I'm not happy. Wire brush and rinse with water and dry quickly.
By needle scaling and wire wheeling first you should then only need one application of gel to get rid of all traces of rust.
However the beauty of epoxy primers is they can cope with residual corrosion left so nowadays I don't use deox much anymore.
I sometimes use strong phosphoric acid on residual rust and rinse off, similar effect but cheaper.
Also read of people mixing in scolacell cellulose powder to strong phosphoric and making a paste/ gel that way.

 

[peterws1957]

Pretty much yes.
Skim off the rust so you have a pitted but otherwise shiny surface.
I find you can get more corrosion out of the craters with a freshly sharpened needle scaler used at an angle to the surface plus low rpm straight bristle wire wheels (I use a cheap right angle air drill).
Apply the deox gel , wait an hour or so to skin off, apply again until you build up a few millimeters thickness then apply cling film. Leave for about 2-3 days, peel back and inspect. At this point I add more fresh deox if I'm not happy. Wire brush and rinse with water and dry quickly.
By needle scaling and wire wheeling first you should then only need one application of gel to get rid of all traces of rust.
However the beauty of epoxy primers is they can cope with residual corrosion left so nowadays I don't use deox much anymore.
I sometimes use strong phosphoric acid on residual rust and rinse off, similar effect but cheaper.
Also read of people mixing in scolacell cellulose powder to strong phosphoric and making a paste/ gel that way.

Yes thanks - I do the same preparation with a needle scaler and wire wheels. My go to rust remover on smaller stuff is citric acid granules, cheap as chips and works in half an hour or so on light rust, overnight on heavier contamination.

 

[Snake Charmer]

Using Deox-C eventually led me to Citric Acid, wonderful stuff. I have a tank that will hold 50 gallons, cast iron engine blocks and cylinder heads come out like new.
I have not tried the gels on sheet metal or bodywork though.

 

[charlysays]

Yes thanks - I do the same preparation with a needle scaler and wire wheels. My go to rust remover on smaller stuff is citric acid granules, cheap as chips and works in half an hour or so on light rust, overnight on heavier contamination.

It's a good combo if you can't sand blast. Even on badly pitted metal, if you spend long enough with the needle gun, keep grinding the needles square/ sharp edge when they blunt/ go rounded then wire wheel from different angles you can achieve a bright clean surface with minimal remaining corrosion which, once roughed up with 40-80g is ideal for epoxy mastic. I've even MIG welded to metal I cleaned up that way and it was fine, no significant spatter issues.
Yeah citric works similarly to deox gel and a lot cheaper. You can use scolacell celly powder to thicken it up to cling to stuff you can't put in a bath.

Sadly Mercs seem to specialise in lots of thick surface corrosion with minimal perforation (although in some cases they do go into big holes- usually 1999-2004 cars in my experience) so techniques like we've developed are vital or you'd end up doing major cut and weld repairs when there's really no need with the right techniques and coatings.

 

[charlysays]

Using Deox-C eventually led me to Citric Acid, wonderful stuff. I have a tank that will hold 50 gallons, cast iron engine blocks and cylinder heads come out like new.
I have not tried the gels on sheet metal or bodywork though.

I think the main ingredient in Deox is citric. Use scolacell to create a gel/ paste with your existing citric acid for a budget option. It doesn't work quite as well but near as damnit. I've also used phosphoric acid with scolacell with good rust removing results but I reckon citric is probably safer.

 

[charlysays]

It wasn’t cut price steel. It also wasn’t as simple an issue as “use cheap materials” for MB.

Firstly. Daimler Group buy all of their commodity metals worldwide under a group purchasing scheme. The metals are bought to highly exacting specifications, and the Group is big enough to represent significant annual steel tonnage in its own right. Daimler buy primarily from the likes of Benteler, Artelor Mittal and ThyssenKrupp, companies not exactly known for shoddy materials.
Secondly, the process by which steel is made somewhat precludes “shoddiness”, as in if a mill is making high quality metals, they won’t (can’t) just stop and switch to making “cheap steel”. The steel is milled, processed and coiled like paper, all in a continuous process. Some mills only make exactly one grade of steel for this reason- they work to the volume limits of their capacity. So, the quality deviations in material that Daimler bought/ are buying to are minimal and subject anyway to Daimler’s own quality standards.

Now we come to the tragic bit, as the Engineer’s Song goes. At some point in the early noughties, some bright spark in MB’s body design team had A Good Idea. The Japanese car designers were doing well with the application of higher quality galvanising to metals in wet areas (cheap) without the need to apply special/ extra paint coats to those areas (very costly). So, MB sought to copy that lead. This was also at the time when the C & E classes saw a huge rise in volume, the E Class rose from 180k to 440k annual worldwide over about 5 years. Put both together and clearly Something Had To Be Done!

So, the body engineering team got to work. Could they be clever about the strategic placement and specification of galvanised steel parts vs paint application?

Quick technical note. Stone rash on wheel arches is solved in Japanese cars by the application of a clear dogleg decal of fairly thick (0.5mm) resilient plastic on top of the paint clearcoat. German cars don’t use these as they feel them to be ugly and less than premium. Also at this point, exterior styling was trending towards a more aggressive road presence, and an easy way to do that is with more pronounced wheel arches.

Add all of this together and you’ll see why the corrosion problem happened. The cars were pretty much designed to rust more easily, without much deeper engineering experience of galv application to corrosion prone areas which at the time, they didn’t have- driven by the need to control costs due to the rapidly increasing volumes generated by the global sales teams.

It should be pointed out that the Japanese experienced their own corrosion problems across the 60s & 70s. It’s nothing unique.

Makes a lot of sense.
I never bought the cheap steel story, or the rust would be in totally random places.
It's not, it always starts with coating damage and/ or in adequate coating/ finishing.
Whatever etch coat MB used it was poor.
My experience of 90s Mercs is the paint is thin and chips fairly easily. Once chipped it rusts rapidly which to me indicates an etch coat issue.
Compare to PSA group cars of the 90s- Peugeot, Citroen etc- you get a chip and can leave it for literally years before a bubble starts. This is because the etch coat is thick and has high zinc content.
Whilst PSA cars can rot a bit in the sills and inner arches you pretty much never see one with significant visible rust unlike Merc.