Bumper Blues

[paul.woodford]

Hi guys, I wonder if someone can me some advice on respraying the bumpers on the SC. I had a new front wing put on a couple of years ago. At that time, the front bumper was exhibiting some bubbling from corrosion, so I had that rubbed down and re-sprayed. It's aluminium, I believe, so I have been surprised that the bubbling has returned after a relatively short period. Does anyone have any advice as to whether special treatment is necessary to inhibit its return, surely a new bumper isn't necessary?

 

[nick3814]

Hi Paul, I have the same problem as you on my 1983 SC and like you presumed as it is aluminium it could be fixed as you describe however I was chatting to the fella who sorts my bodywork out the other week and he said once aluminium gets corroded its virtually impossible to get rid of it other than cut it out and re weld a piece in, and welding aluminium is a pig of a job.
The advice he gave as he has repaired these in the past is to cut it out and attach glass fibre/resin to it, he knows of one bumper he sorted some five years ago and it still looks like new, so maybe this is something you might want to try.

Cheers

 

[Guest]

You can light media blast the bumper to get it back to bright and then use two pack etch primer on it before base primer and top coat, same as painting boats. That finish is usually good for years. Mine a bit chipped in places too and will go down that road when it gets to the top of the 'put-right' list.

The more primer you use the better, six or seven coats usually stops damage like stone chips from getting back to the metal and opening it up to oxidation again in the future.

 

[Bazgillie]

The old rear bumper on mine had started to delaminate where the corrosion had got in. I managed to find a pair of bumpers on E-bay and they where the right colour. have you tried any of the breakers the bumper must be the same right through to the end of 3.2 production. Also on E-bay at the moment is a pair of RSR fiberglass bumpers.
Baz

 

[Guest]

I have an old 3.2 rear bumper in the garage. It would need prepping as per John's comment above but £25 if anyone is interested.

 

[paul.woodford]

Thanks all. I would very much like to retain the bumpers rather than change them so maybe the best approach is remove as much corrosion as possible with a blast treatment. The bubbling itself isn't bad - much less unsightly that rust bubbles - but it obviously needs to be dealt with at some point..

BTW I'm new to the forum and note that where my profile details are shown on my initial message, it shows me as a non-member. I filled in my membership number on my profile - so what am I doing wrong? I see I also only have one star, which I am slightly miffed about, but there again that's how it was at school.
paulw

 

[RSGulp]

Paul,
Welcome to the forum. Check out this link to remedy the 'non member' problem.
Gen Discussion - Why does it say Non Member?

The number of stars is a bit like McDonalds. The more you turn up and contribute, the more stars you get. Once you've mastered fries you'll be allowed to flip burgers.

Have a nice day!
Rich

 

[paul.woodford]

Rich, many thanks. Now I just need to spend some time (oh and money) getting my car up to par with the rest of you..............
paulw

 

[Guest]

The problem with the rear impact bumpers is actually in the design. Why Porsche decided to attach the rear valance to the bumper using steel scews straight into the aluminium is a mystery to me. Dissimilar metals, add moisture, hey presto - your bumper becomes a battery. This causes 'galvanic corrosion' - which is why you will find 'volcanoes' erupting around the screws on the inside of the bumper. It doesn't 'delaminate' as such - it's called 'exfoliation' and layers of ally will peel off.
New bumpers cost around £800 quid.
I bought a decent used one and ground out most of the corrosion - hopefully wth a good acid-etch and paint, it will do me for a few years.
Another thing - my car is a late 3.2 - the replacement bumper is from an SC. Differences are the SC one doesn't have the tow-eye, but I also found that the cut-out along the lower edge for the silencer is slightly smaller - I have yet to see if it will need clearancing for my silencer. I don't know if it is bigger than an SC one.
Hope this is of some use. []

 

[Guest]

Hi Paul,
I have successfully repainted both front and rear bumpers and all the attached bobywork you remove to get the bumpers off on my 1883 SC and I have had no problems with recurring corrosion since. Like you I wanted to keep my original bumpers, all the blisters and chips made my bumpers look terrible but with a little elbow grease and a lot of patients you will be surprised at the results.
All I did was buy a propper rubber sanding block and used wet and dry 600 , followed by finer papers up to 1500 grade all available from Halfords, I did not remove good paint and undercoat just rubbed it down ready for priming. Any pits I could not remove by rubbing down were filled with Chip and dent repair filler from Halfords.The actual amount of filler was minimal vertually nothing. The key to this repair job was patients and always using the rubbing block when rubbing down.
I took one of the unprepared small panels to a paint shop to have the colour matched , this was very successful.
Hope this helps
John

 

[paul.woodford]

Thanks for that John, it sounds as though the corrosion can be treated successfully if one is prepared to work hard enough at it.

 

[Guest]

Hi Paul,
You got it in one hard work will pay dividends.
I should point out that I am not a body shop or spray man I just approached the job as a project.

You probably know all of this but here are a few tips.

I would recommend you buy a heat gun or hot air blower the type you use to strip off wall paper, you will find this very helpful when drying the bumpers after rubbing down with wet and dry and prior to painting.(B&Q sell these) Also prior to painting I used metholated spirit to clean any residual grease from the surface to be painted.
To do this work I turned my garage into a spray shop and used electric heaters to ensure the garage was worm not gas heaters which give off moisture. I put plastic sheeting on the ceiling of the garage and over any draft areas.

The most important thing is to use a mask when spraying.

Cheers for now
John