Paint and corrosion

[Dieselman]

Further to gary's comment I will share a little info.

John my dealer told me that corrosion problems that MB had and not just the E class was being put down to the change and thinness of the new paints, not to sure on that I would have thought the initial protection would have been at fault, anyway they say its all OK now, suddenly his nose grew another 4 inches.

gary

It is a sad fact that all MB products suffer corrosion due to poor build quality and paint application.

Some areas of the bodies are poorly stamped out leaving sharp edges which are either unpainted or the paint can't sufficiently cover. This is where most of the corrosion starts, think about it it's always joints and seams.

We are all aware of the corrosion affecting late '90s cars, which affects the whole range including aluminium bodied CL cars.

Strangely the humble A class appears to be the best performer, I have a thought on this.

If the paint thickness is measured on a late '90s car it will be in the region of 60-100 microns thick varying across the body. Thats primer, colour coat and clear lacquer. Pretty thin. Remember ther are 1000 microns to a millimetre.

This is due to two things; one, waterbased paints are slower drying so are more likely to run if applied too thick, and two, the colour can now be achieved in a single coat so MB save a significant amount of money by applying only one coat.

Post new century cars appear to have a thicker paint coat of about 80-100 microns but from approx '02 have had seam sealer deleted from the joints.

Post late '04 cars now have galvanising and seam sealer back on the joints to stop corrosion. The measured thickness on these cars is about 110 microns due to even paint application and the zinc plating adding additional thickness.

Some cars have aluminium panels to save weight, but be aware that aluminium does corrode if exposed to water.

On a particular current model with aluminium front wings, bonnet and boot check the boot skin to frame joints carefully. Due to the lack of seam sealer water is entering the joint and causing corrosion. (you can see I'm being very diplomatic here )

I have a theory that metallic paint may offer lesser protection due to containing the metal chips, whereas soid colour cars the whole paint thickness is made up of paint which is therefore more flexible.

Regarding the A-class. As it is the budget MB, maybe more of them are specified with solid colour than other models, hence as a range it is more tollerant to poor application.

 

[SSBB]

I just got my E300TD back (yesterday) after MB replaced the front wings and drivers door, the boot was repaired as were the rear wheel arches. The bonnet had over 30 rust blisters but MB refused to repair stating they were stone chips (even though no paint was missing) so I done a deal with their approved repairer and the whole lot was done and now looks fantastic.
Im seriously thinking of getting rid and replacing with a C250 TD estate in flat blue before the rust comes through again. I bought the car with a full MB history but cant afford their servicing costs so no more warranty claims!!
I used to own an eight year old Nissan Almera 90,000 miles and no rust...whats going on with MB

 

[Tiff]

Perhaps they could take a lesson from the French...I don't know how they do it,but French cars in general seem very corrosion resistant,which surprises me as they seem to be made of very thin steel,and aren't galvanised.I wouldn't say they have any better paint or underbody protection than any other make of car either.I have yet to weld up a Citroen Xantia,Peugeot 306 or similar cars,even from the early 90's,and very few you see on the road are rusty,even when obviously neglected.

After owning 2 Mercs, and being in the motor trade,I have become very aware of Mercedes rust problem.I had to respray my W202 due to corrosion,even though it had been a cherished car,and it was obvious that the rust had come fro the inside,and not caused by stonechips etc.My current W124 has rotten front wings,even though the rest of the car is immaculate.Its an obvious design fault,as every 124 I see now has the same problem.I have no personal experience of the newer models,but have found even earlier cars to have a rust problem,before water based paint/no sealer/thin coverage.

I reckon Merc should come clean and admit its poor quality steel.Fiat and Lancia had issues with this in the '70's and '80's,caused by very poor quality steel supplied by the Russians.I once spoke to someone who had inside knowledge of the problem.They say the Russin steel,during production,did not have the "scum" and oxidisation removed when being made,so the rust was actually in the steel.You could put 1000 coats of paint and underseal on these cars,and they'd still rot.This chap actually remembers a Mirafiori being delivered to his dealership,brand new,with a rust blister the size of a dinner plate in the centre of the roof.

The Lancia brand(which I love) was killed off in the UK due to this problem,but they did the decent thing,admitted there was a problem,and never really recovered.Mercedes seem to be trying to worm their way out of warranty claims and denying any knowledge that its a trend that seems to be getting worse. How long is this going to go on before everyone starts buying Lexus and Audi?? After reading some horror stories on various forums,I certainly would think more than twice about spending 20-40K on a car that has "rust issues" Lancia have never recovered from that Daily Mail story,and its the first thing people say when discussing the brand.Will it be Mercedes turn in a few years??

 

[big x]

Perhaps they could take a lesson from the French...I don't know how they do it,but French cars in general seem very corrosion resistant,which surprises me as they seem to be made of very thin steel,and aren't galvanised.I wouldn't say they have any better paint or underbody protection than any other make of car either.I have yet to weld up a Citroen Xantia,Peugeot 306 or similar cars,even from the early 90's,and very few you see on the road are rusty,even when obviously neglected.

After owning 2 Mercs, and being in the motor trade,I have become very aware of Mercedes rust problem.I had to respray my W202 due to corrosion,even though it had been a cherished car,and it was obvious that the rust had come fro the inside,and not caused by stonechips etc.My current W124 has rotten front wings,even though the rest of the car is immaculate.Its an obvious designfault,as every 124 I see now has the same problem.I have no personal experience of the newer models,but have found even earlier cars to have a rust problem,before water based paint/no sealer/thin coverage.

I reckon Merc should come clean and admit its poor quality steel.Fiat and Lancia had issues with this in the '70's and '80's,caused by very poor quality steel supplied by the Russians.I once spoke to someone who had inside knowledge of the problem.They say the Russin steel,during production,did not have the "scum" and oxidisation removed when being made,so the rust was actually in the steel.You could put 1000 coats of paint and underseal on these cars,and they'd still rot.This chap actually remembers a Mirafiori being delivered to his dealership,brand new,with a rust blister the size of a dinner plate in the centre of the roof.

The Lancia brand(which I love) was killed off in the UK due to this problem,but they did the decent thing,admitted there was a problem,and never really recovered.Mercedes seem to be trying to worm their way out of warranty claims and denying any knowledge that its a trend that seems to be getting worse. How long is this going to go on before everyone starts buying Lexus and Audi?? After reading some horror stories on various forums,I certainly would think more than twice about spending 20-40K on a car that has "rust issues" Lancia have never recovered from that Daily Mail story,and its the first thing people say when discussing the brand.Will it be Mercedes turn in a few years??

Good post Tiff.One thing I would add is cars from Scotland and mountain areas of Wales have much worse corrosion underneath than most English cars due to more road gritting.The MOT guy I use confimed this saying he could tell where a car was registered just by looking underneath ! I've seen E32 BMW's from Scotland that looked like old trawlers

...everything underneath rusted solid.My own 1992 740i which spend most of it's life in Surry has no rust anywhere.I also noticed that whilst stone chips go through the clear coat and metalic red paint none has ever penetrated the flat red paint undercoat.Even if it did the did the bonnet is galvanized.These cars have their fair share of mechanical and electrical problems but like most makes rust has long ago been defeated and is just not an issue.

adam

 

[Shude]

One of the reasons for MB paint woes is that they are constantly leaned on and penalised for use of chemicals in their factories and processes. This is why the early-mid 90s wiring harnesses "bio-degraded" and why paint has been applied in very thin layers on some models.

The Germans are obsessed with the use of chemicals, for example it's illegal to wash a car or carry out any kind of mechanical work on the street in Germany, in case oil or other chemicals are spilled. Ever tried the Karcher car-wash or house/patio solutions that are included? They're useless and almost all water!

Probably great for the environment though.

 

[glojo]

On a particular current model with aluminium front wings, bonnet and boot check the boot skin to frame joints carefully. Due to the lack of seam sealer water is entering the joint and causing corrosion. (you can see I'm being very diplomatic here )

Certainly no need to be diplomatic... Only the legal profession will defend the indefensible!

Have you any idea how these figures relate to other manufacturers? Do manufacturers make there own paint or is it supplied by a paint manufacturer? I am NOT attempting to defend anyone here, I am merely trying to get a full picture.

The steel that is used...... Do different factories source there own steel or has Mercedes-Benz got a bulk contract from one supplier? I only have a limited knowledge of the different countries that actually produce Mercedes-Benz and I have visions of the steel being perhaps sourced from varying locations, but that is merely an observation?

Do you believe that tailgates of this current model with aluminium front wings, bonnet and boot (copied and pasted ) are also vulnerable to this problem and would you advise removing the inner panel and squirting in some protective 'gunge'?

It also looks like manufacturers are taking turns in buying very poor quality cheap steel?? Ford, Vauxhall in the sixties, Fiat, Lancia in the seventies, Datsun in the eighties, now perhaps Mercedes-Benz in the nineties (although I take very seriously the informative post by Dieselman and I am extremely interested to hear if anyone knows the thickness of paint applied to other brands)

Yours respectfully
John the thick skinned and no rust

 

[230K]

Further to gary's comment I will share a little info.



It is a sad fact that all MB products suffer corrosion due to poor build quality and paint application.

Some areas of the bodies are poorly stamped out leaving sharp edges which are either unpainted or the paint can't sufficiently cover. This is where most of the corrosion starts, think about it it's always joints and seams.

We are all aware of the corrosion affecting late '90s cars, which affects the whole range including aluminium bodied CL cars.

Strangely the humble A class appears to be the best performer, I have a thought on this.

If the paint thickness is measured on a late '90s car it will be in the region of 60-100 microns thick varying across the body. Thats primer, colour coat and clear lacquer. Pretty thin. Remember ther are 1000 microns to a millimetre.

This is due to two things; one, waterbased paints are slower drying so are more likely to run if applied too thick, and two, the colour can now be achieved in a single coat so MB save a significant amount of money by applying only one coat.

Post new century cars appear to have a thicker paint coat of about 80-100 microns but from approx '02 have had seam sealer deleted from the joints.

Post late '04 cars now have galvanising and seam sealer back on the joints to stop corrosion. The measured thickness on these cars is about 110 microns due to even paint application and the zinc plating adding additional thickness.

Some cars have aluminium panels to save weight, but be aware that aluminium does corrode if exposed to water.

On a particular current model with aluminium front wings, bonnet and boot check the boot skin to frame joints carefully. Due to the lack of seam sealer water is entering the joint and causing corrosion. (you can see I'm being very diplomatic here )

I have a theory that metallic paint may offer lesser protection due to containing the metal chips, whereas soid colour cars the whole paint thickness is made up of paint which is therefore more flexible.

Regarding the A-class. As it is the budget MB, maybe more of them are specified with solid colour than other models, hence as a range it is more tollerant to poor application.

Hi


Check out the paint thickness on my 98 210 bonnet frame (note rust just beside) and then check paint thickness on the wifes 93 124.

Definitely more paint on the early cars.

230K

 

[glojo]

Hi


Check out the paint thickness on my 98 210 bonnet frame (note rust just beside) and then check paint thickness on the wifes 93 124.

Definitely more paint on the early cars.

230K

Trouble is you are comparing chalk and cheese, or oil and water .

One is a good old fashioned cellulose paint and one is water based.

John

 

[230K]

Trouble is you are comparing chalk and cheese, or oil and water .

One is a good old fashioned cellulose paint and one is water based.

John

Yes but one was good and one is bad.

230K

 

[Tiff]

One is a good old fashioned cellulose paint and one is water based.

I don't think cellulose paint has been used for new cars since the '70's???

One thing I would add is cars from Scotland and mountain areas of Wales have much worse corrosion underneath than most English cars due to more road gritting.

This is true,and even more so when you get a car from a coastal village,they may look OK on top,but the salt spray,and corrosion get everywhere,and can look HORRIBLE underneath.I run Fiat X1/9's,and usually take then off the road during winter,and have never had any rust problems at all,this year I ran it for a month,and its bubbling up in quite a few places,even though I tend to hose down underneath the arches etc,very regularly.I also work right on the seafront,and the car is parked right across the road from the sea....does anywhere else have so much coast,dampness and grit than the UK?...BUT,were mising the point here,see my earlier post about French cars,how do they do it?

 

[glojo]

They stopped using cellulose in the 70's? Crikey me time flys.

Way back in the 80's a friend of mine from Guernsey had a three year old Volvo, and the rust on it was horrendous. I wonder if this was a common problem or a one off? We are on the coast, but rust has never appeared to be any worse than on other cars from further inland? In the summer months we tend to get a very fine powder type dusting on our vehicles which is blown all the way across from the Sahara.

John

 

[Shude]

Can someone explain to me how the modern paints can genuinely be "water-based" please.

 

[glojo]

Can someone explain to me how the modern paints can genuinely be "water-based" please.

What a great question.

I enjoy being a member of this forum and one of the reasons is that it is a great place for expanding your knowledge. As a result of Shudes question I have started researching the answer and am surprised at what I'm finding out.

If I am reading things correctly (this doesn't answer Shude's question) more paint is applied on a water based car than a solvent one? The water based car spends more time in the oven (simply because the paint takes longer to go off)

http://www.3daycar.com/mainframe/publications/library/Painting3DC.pdf

Sorry it's a PDF file and I'm carrying on with the research.

I still can't get my head around Tiff's bombshell of 1970's being the time all manufacturers changed over. I am NOT disputing this but find it strange. The first car we owned that suffered terribly from the usual small stone chipping was the 210 E-class.

Off surfing again,

John

Just sent an e-mail off to a major paint manufacturer

 

[Tiff]

I remember my dad's 1970 Viva HB was new fangled metallic acrylic,so it was probably the early '70's! It was Aqua Starmist,a beautiful coulour.really stood out amongst the greys and browns of the '70's!!!

Here's some info...

Acrylic lacquer was used extensively by General Motors. Acrylic Enamel: During the late 1960's and early 1970's, technology brought on the development of acrylic enamel, which was harder and more durable. Chemically, it is a cousin to synthetic enamel, but is modified with acrylic resin, and is not soft and sticky with no solvents present. It cures further with the absorption of oxygen from the air. Unlike the lacquers, which remain soluble in solvents, the enamel family is insoluble in solvent when cured. An acrylic resin is chemically any polymer whose basic monomers are chemical derivatives of acrylic acid. Polyurethane Enamel: In the mid 1970's, polyurethane enamel was developed to withstand the severe stress of high speed airplane surfaces, which are subject to rapid temperature changes and flexing. This paint was much more durable than the acrylic enamels. Acrylic Urethane Enamel: Acrylic urethane enamels were developed to withstand environmental elements, such as acid rain and ultra violet rays. It is the most durable paint to date.

 

[Dieselman]

Tiff is about right with the cellulose paints age. After that manufacturers went to two pack acrylic as it gives a better finish and is harder.

Water based paints are effectively emulsion paints, where as solvent paints are quick drying solvent suspension paints. In both cases the paint itself is acrylic.

 

[Dieselman]

Hi


Check out the paint thickness on my 98 210 bonnet frame (note rust just beside) and then check paint thickness on the wifes 93 124.

Definitely more paint on the early cars.

230K

Not a good comparison. The door of the W124 is a fully finished panel and the bonnet frame on the W210 is only primer and colour. In adition it is a part that relies on overspray for it's application.

Test two similar flat panels.

I was surprised when measuring a W124 coupe that the paint was only about 110-120 microns.

 

[Dieselman]

Have you any idea how these figures relate to other manufacturers? Do manufacturers make there own paint or is it supplied by a paint manufacturer? I am NOT attempting to defend anyone here, I am merely trying to get a full picture.

The steel that is used...... Do different factories source there own steel or has Mercedes-Benz got a bulk contract from one supplier? I only have a limited knowledge of the different countries that actually produce Mercedes-Benz and I have visions of the steel being perhaps sourced from varying locations, but that is merely an observation?

Do you believe that tailgates of this current model with aluminium front wings, bonnet and boot (copied and pasted ) are also vulnerable to this problem and would you advise removing the inner panel and squirting in some protective 'gunge'?

It also looks like manufacturers are taking turns in buying very poor quality cheap steel?? Ford, Vauxhall in the sixties, Fiat, Lancia in the seventies, Datsun in the eighties, now perhaps Mercedes-Benz in the nineties (although I take very seriously the informative post by Dieselman and I am extremely interested to hear if anyone knows the thickness of paint applied to other brands)

Yours respectfully
John the thick skinned and no rust

I don't think the problem is the base metal, it's the subsequent protection.

Think about this. all members cars have suffered at the edges of panels, not in the middle of painted areas.

I would carefully check all exposed edges for evidence of seam sealer an would sqirt rustproofing oil or wax into the cavities.

When waxing a car always do the door shuts and inner leaves. This will seal the paint in any porus areas.

 

[Dieselman]

Perhaps they could take a lesson from the French...I don't know how they do it,but French cars in general seem very corrosion resistant,which surprises me as they seem to be made of very thin steel,and aren't galvanised.I wouldn't say they have any better paint or underbody protection than any other make of car either.I have yet to weld up a Citroen Xantia,Peugeot 306 or similar cars,even from the early 90's,and very few you see on the road are rusty,even when obviously neglected.

This is very true. French cars, particularly Peugeot/Citroen do not rust.

They certainly used to treat the steel bodies very thoroughly by using cleansing baths and phosphate dipping.
After that they use proper underbody protection and anti stone chip paint. lastly they use cavity wax inside closed areas.

MB don't do any of this.

 

[glojo]

Can someone explain to me how the modern paints can genuinely be "water-based" please.

Hi Shude,
I went off and asked the experts , "What is water based paint" and as a follow-up, I asked if the paint can be diluted with water and of course can the equipment also be cleaned with water?

and, "When did it become compulsory for car manufacturers to use it?"

Here is the reply:

Dear John

To answer your easiest questions first:

Paints normally contain some volatile material. This is in order that the
paint is thin / runny enough to be applied by brush / roller / spray. Once the paint has been applied, this volatile material evaporates to leave a film that then dries.

If the volatile material is organic (i.e made up of compounds largely based on carbon and hydrogen) then we refer to the coating as a solvent based paint.

The solvents (materials like white spirit, xylene, butanol etc) are often
referred to as volatile organic compounds (VOCs).

If the volatile material is mainly water we referred to the coating as a water based paint. In fact many water based paints also contain some VOCs. Emulsion paints are one example where small amounts of VOCs (known as co-solvents) are added to aid in the coalescence of the emulsified resin during the drying process.

In general water based paints can be diluted with water and water can be used to clean brushes etc used with such paints. Whether or not water SHOULD be added to a water based paint is something that the manufacturer can advise on.


Now to deal with your question regarding when water based paints become mandatory. As I understand the situation, nobody has said "You must use water based paints". What the have said in effect is:-

"You must limit the amount of VOCs emitted by your painting process" The
details are given in the Solvents Emissions Directive.

AND

"You must limit the VOC content of your paints" The details are given in the Paint Products Directive.

These are both complex documents but if you need help in locating them please let me know.