aluminium rot

[teflon2]

Sorry in advance if this has been raised before but tried to locate previous threads but couldn't. I have several small bumps on the aluminium sides of my 12 year old Autosratus I am looking for any product that will prevent it spreading if after cleaning and priming the areas it turns out to be not enough. Rather like the fluid that is used to alter the structure of rust. Thanks in advance John. :-|

[Dave Newell]

If the aluminium skin of your motorhome has started to corrode the chances are its doing from inside out due to water ingress into the timber structure. When wood suffers wet-rot it gives off chemicals that will eat through aluminium.

 

D.

[colin]

Alumiprep and Alodine is your best bet to try to hold it back, but proboly won't give a perminant solution esp. if it is as dave says, or there are joints and/or screw holes.

p.s. what sort of primer did you use?

[teflon2]

thanks for the comment but pitting is from the outside inwards. Possibly because that side is parked close to conifers and subjected to passing sugar beet loads and fumes ie. sugar factory is across the road. :-S

ps they also have anti odour fume spraying outlets.

[dikyenfo]

The problem is the grade of ally that is used. To prevent grot the ally has to be subjected to several processes and these are not done for lower grades such as used on MH's.

Things like brake valves/control valves and brake chambers are subject to salt spray tests and must pass to be used on commercial vehicles.

Unfortunately no regs. are done for our ally. Replacement is all you can do if possible.

[teflon2]

Thank you Colin just what I needed to know, Haven't started the work yet waited untill I found out what to use as an inhibitor once I began because as soon as I expose the areas I want to be able to treat it imediately as to primer I was considering one of the aluminium touch up paints as a furst coat. The spots are very small and there are only 5 of them 4 about 2mm diam. the other about 5mm x 2mm, no screws or seams local and the nearest window is about 1meter away. Thanks to everyone who answered allthe best. John :-)

[Brambles]

The usual way to treat corroded aluminium is to mechanically remove as much corrosion as possible..the powdery oxide.

Then treat with a 10% solution of sulphuric acid or chromate acid or even a mixture of the two, Propriority treatments are available. You need to be careful and sort of know what you are doing. Brush the solution on and work well into the pitting with a stiff brush. Wear usual protective gear etc.

Leave on to work for 5 to 10 minutes and wash of thourally. Obviously you will want to protect the surrounding area. After washing thourally let it dry completely. If the pitting is right through the panel then you need to be very careful acid will not penetrate right through.

At this time of year you will need some heat to help get completely dry if alloy is pitted and has any voids or fisures. Hair dryer will suffice

Next step is to use an etching primer suitable for aluminium. This will etch the surface of the aluminium as it cures and form a good bond. Work well into any pitted areas and leave to cure and harden.

Then you can fill and finish in normal way.

If you are struggling to get a small quantity of edging primer you could take a short cut and use epoxy resin (araldite 24 hour) to fill the pitting and to seal the aluminium. Epoxy adhesives bond extremely well to aluminium and were initially developed to bond aluminium alloys.

Hope my penny worth helps.