How to treat electrical connector corrosion?
Discussion
The check control computer in my 1992 BMW 730i has started occasionally complaining that my licence plate lights have failed, but they do light up dimly when the sidelights or headlights are on.
Today I took out the licence plate light units which live on the underside of the boot lid, and sure enough the bullet-shaped bulbs themselves are blackened. More problematic however is the state of the metal spring clips which supply the bulbs. They're covered in green corrosion, and the plastic lenses are covered in a dusting of the green stuff. I think I've caught it in reasonably good time, as the metal connectors are still strongly springy and don't look like they're about to corrode into thin air.
So what's the best way to treat the corrosion? The metal spring connectors are very difficult to remove from the plastic lens, which means that using sandpaper or a Dremel will work to clean the parts that contact the bulbs, but won't get rid of the corrosion from the parts I can't reach. A bit of Googlage suggested that some sort of weak acid might work, so I've filled up a glass with vinegar and have them soaking in there. They've been in there a couple of hours and I'm not seeing much change yet, but perhaps they need more time?
Are there any better methods, either using household cleaners or commercial products that will do this job? I do have a can of Deoxit spray contact cleaner, but I don't think that'll do much against the green stuff!
It looks like I can probably order some new lights (BMW part number 63261388927) but they may be about £30 each. If I can avoid spending £60 on new lights, so much the better!
Today I took out the licence plate light units which live on the underside of the boot lid, and sure enough the bullet-shaped bulbs themselves are blackened. More problematic however is the state of the metal spring clips which supply the bulbs. They're covered in green corrosion, and the plastic lenses are covered in a dusting of the green stuff. I think I've caught it in reasonably good time, as the metal connectors are still strongly springy and don't look like they're about to corrode into thin air.
So what's the best way to treat the corrosion? The metal spring connectors are very difficult to remove from the plastic lens, which means that using sandpaper or a Dremel will work to clean the parts that contact the bulbs, but won't get rid of the corrosion from the parts I can't reach. A bit of Googlage suggested that some sort of weak acid might work, so I've filled up a glass with vinegar and have them soaking in there. They've been in there a couple of hours and I'm not seeing much change yet, but perhaps they need more time?
Are there any better methods, either using household cleaners or commercial products that will do this job? I do have a can of Deoxit spray contact cleaner, but I don't think that'll do much against the green stuff!
It looks like I can probably order some new lights (BMW part number 63261388927) but they may be about £30 each. If I can avoid spending £60 on new lights, so much the better!
Get a small amount of dried citric acid, mix it with water at a ratio of 17 water to 1 citric acid in a plastic bowl, warm water.
Leave to soak overnight, then rinse off with warm running water and an old toothbrush.
Dry, and then spray with a light oil like 3 in 1.
Should sort it out. In fact it will dissolve rust on anything that's not greasy or oily. It will do surface rust really well, any flaky rust needs removing before soaking.
Eta, link.
https://www.ebay.co.uk/itm/403989695535?mkcid=16&a...
Leave to soak overnight, then rinse off with warm running water and an old toothbrush.
Dry, and then spray with a light oil like 3 in 1.
Should sort it out. In fact it will dissolve rust on anything that's not greasy or oily. It will do surface rust really well, any flaky rust needs removing before soaking.
Eta, link.
https://www.ebay.co.uk/itm/403989695535?mkcid=16&a...
Edited by Getragdogleg on Saturday 25th February 16:03
LunarOne said:
It’s not actually rust though. I think it’s copper oxide. Does that make a difference?
I find it removes oxides and leaves bare metal. It won't remove paint or damage plastic so it is gentle.I toss tools in it from time to time, Allen keys and impact sockets come out brand new looking.
Thanks for that. I'll keep that in mind for next time. I went out to run some errands today and when I got back, I checked and it looks like the vinegar has worked. Perhaps because I put the glass with the vinegar and connectors in the microwave for a minute to warm them up. Anyway the green stuff seems to have turned black, and the buffing the metal parts has revealed coppery parts underneath where there was some sort of silver-coloured plate - perhaps nickel?
Anyway I've dried everything out thoroughly, put in two new bulbs and everything is working as it should - the plastic lenses are clear and the bulbs are bright!
Anyway I've dried everything out thoroughly, put in two new bulbs and everything is working as it should - the plastic lenses are clear and the bulbs are bright!
GreenV8S said:
If you have corroded connectors, check the state of the wiring too - if corrosion has started, it can quickly travel a long way under the insulation leading to the dreaded black wire syndrome.
That would be a pain as you need to cut back so much of the loom and replace….unless there is a remedy?Above, various acids have been recommended, oxalic, citric, vinegar(acetic), etc. The point is that the activity of an acid depends on the extent that it ionises in water, its "equilibrium constant". A 'strong' acid, like hydrochloric is highly ionised and is in the group of "strong" acids, like sulphuric, an these will attack the native metal as well as any corrosion, so are useless for this purpose.
The "Weak" acids are mainly organic as in the above list, and almost any organic acid will dissolve corrosion more easily than the native metal. An exception is phosphoric acid, because iron phosphate is almost insoluble in water, so that a layer of that forms on the surface of the rust. This makes phosphoric the basis for most 'rust conversion' products, as if thick rust is removed first, once dried the phosphate forms a good foundation for other coatings.
But don't use Coke! It does have phosphoric acid in it, it provides the 'bite' taste, but in a fraction of a percentage concentration.
John
The "Weak" acids are mainly organic as in the above list, and almost any organic acid will dissolve corrosion more easily than the native metal. An exception is phosphoric acid, because iron phosphate is almost insoluble in water, so that a layer of that forms on the surface of the rust. This makes phosphoric the basis for most 'rust conversion' products, as if thick rust is removed first, once dried the phosphate forms a good foundation for other coatings.
But don't use Coke! It does have phosphoric acid in it, it provides the 'bite' taste, but in a fraction of a percentage concentration.
John
tapkaJohnD said:
Above, various acids have been recommended, oxalic, citric, vinegar(acetic), etc. The point is that the activity of an acid depends on the extent that it ionises in water, its "equilibrium constant". A 'strong' acid, like hydrochloric is highly ionised and is in the group of "strong" acids, like sulphuric, an these will attack the native metal as well as any corrosion, so are useless for this purpose.
The "Weak" acids are mainly organic as in the above list, and almost any organic acid will dissolve corrosion more easily than the native metal. An exception is phosphoric acid, because iron phosphate is almost insoluble in water, so that a layer of that forms on the surface of the rust. This makes phosphoric the basis for most 'rust conversion' products, as if thick rust is removed first, once dried the phosphate forms a good foundation for other coatings.
But don't use Coke! It does have phosphoric acid in it, it provides the 'bite' taste, but in a fraction of a percentage concentration.
John
Very useful info. I don't think most people have sulphuric or hydrochloric acid knocking about at home. I certainly don't - but it's still handy to know.The "Weak" acids are mainly organic as in the above list, and almost any organic acid will dissolve corrosion more easily than the native metal. An exception is phosphoric acid, because iron phosphate is almost insoluble in water, so that a layer of that forms on the surface of the rust. This makes phosphoric the basis for most 'rust conversion' products, as if thick rust is removed first, once dried the phosphate forms a good foundation for other coatings.
But don't use Coke! It does have phosphoric acid in it, it provides the 'bite' taste, but in a fraction of a percentage concentration.
John
This is quite expensive, but what I used to prevent corrosion on my connectors, its very good.
https://www.autoelectricsupplies.co.uk/product/827...
https://www.autoelectricsupplies.co.uk/product/827...
Mr MXT said:
This is quite expensive, but what I used to prevent corrosion on my connectors, its very good.
https://www.autoelectricsupplies.co.uk/product/827...
That looks very much like dielectric grease, which would probably do the same job... I bought the tube of dielectric grease for about £5 for use when fitting new ignition coils to my Boxster. I can't pack the light fittings with grease, but I could put some in the connectors themselves which aren't yet corroded...https://www.autoelectricsupplies.co.uk/product/827...
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