Rust Detection

Hmmmm is it possible to wipe these spots off the painted surface and show that the paint is intact and not rusty?

Does that prove that the corrosion is after it is installed and is due to contamination?

Is the customer complaining that the rust spots were because of your fault... i.e. supplying contaminated paint??

I'm not sure I'm following this at all... John.

Thanks for the fast responce. - Regarding wiping the spots off - I can presume the field personel have tried that - but will ask. I would agree that if you could wipe the spots off that the contaminates were post shipping. In the event they do not wipe off I was looking for some sort of field test that would verify that is was infact an iron oxide as opposed to some other contaminate exhibiting the same orange/red tinge.

It is possible the customer is hinting the defect came from the supplier. I have only recieved the first report of the problem and have not seen this defect reported in the past. We only use aluminum and SS metals in our product along with 2 mils of Powder coat paint - this failure mode has never surfaced. Ive checked the process eliminating any probable/possible contamination in the assembly stages.

I'm thinking there is a quick field test to verify the partical in the contaminate (other then magnets) is a ferrous metal. In this case there is no visable solids that could be picked off with a magnet - only the residue indicating that it may have been ferrous metal. Give our lack of experience in dealing with this failure mode It seemed faster to ask those who experienced similar defects..... Tom

Just run a magnet over the spot. Look at the magnet. Does the magnet show these "dots". If it does, the indication is that someone nearby was grinding or welding ferrous metal. Clean away these spots and touch up the aluminum painted surface if was damaged. Aluminum will not be attracted to the magnet.

Ferrus oxide will not be attracted to a magnet either, I think?

John.

Correct.

Thanks for the response - Ther are no solids I can see in the picture that could be pick off by a magnet.

I'm a bit rusty (excuse the pun) on chemistry, but I think you could lightly spray the surface with something that will react with the oxygen in the rust. You would want to use something that would produce a visible reaction, so that a field hand could use it.

Correct - I believe I have a response that has provided the answer --Thanks

Mate,

Try using a rust converter. It is basically concentrated phosphoric acid. Turns iron oxide into iron phosphate. you will notice virtually straight away. Cheap.

Try Septone Rust Converter. Cheap about $10-20 a 250ml bottle, from your local car parts store

Used it on my EJ Holden Station Wagon. Just be careful about using it as it may fade you duco if your not careful about spills, or drops.

Thanks - I believe this would correct the problem and provide evidence the stain is infact iron oxide. I suspcet we could swab some on the surface to performt he test.

Thanks for your information

The Potassium Ferricyanide test is old but reliable. There is some information here.

http://www.waterjetting.org/test.htm

The Potassium Ferricyanide solution should turn the brown spots blue very quickly if in fact they are rust.

Thanks for the info - I checked out he site - very interesting approach. will pass this on to our field rep.

what is the possibility of using a rust remover such as oxalic acid?

I will look into this - thanks