Melting marks on plastic housings

[plazma]

I have bought some items like C64C, 1541-II with weird melting marks on the housing. Like some one had drawn a line with a soldering iron etc.
They are in fact caused by wrapping cables around the housings and storing for a long time. The PVC jacked on the cables have softener chemicals to make the cable flexible. If the cable is in contact with ABS or PVC housings the chemicals may melt the plastics.

I've had also some blue PVC gloves (like these http://www.glovesnstuff.com/_0_0_419FE.jpg) melt all kind of plastic stuff if stored side by side.

 

[thecellartroll]

Thanks for the info. I've seen these marks before and always wondered what caused them when it seemed unlikely the previous owner used a soldering iron.

 

[roy_bates]

wow,ive just offered something via pm that looked like Frankenstein.
but,im pretty sure the thing i have is due to a soldering iron.

 

[Bryce]

That's why I always keep the cables seperate from the machines. And wind the PSU cables in a seperate loop rather than around the PSU.

It's quite easy to see whether it's a cable melt or solder burn. The cable melts are usually very smooth and symetrically curve into the plastic. A solder burn usually blackens the plastic and causes tiny bubbles to form making it feel much rougher.

Bryce.

 

[demolition]

That is very nice to know. I got some C64s with several of those marks and wondered how someone managed to be so careless with the soldering iron. Now I know.

I generally store machines in one place and cables in another, and I also take things out regularly so they don't get to sit for years without moving, so I hope I can avoid any mishaps like that.

 

[AndyLandy]

Oh wow! Learn something new every day.

Note to self, stop wrapping cables round things for storage!

 

[Merlin]

[Science bit]

Older PVC masterbatches would have used phthalates such as Di Iso Octyl Phthalate or Di Butyl Phthalate to make them flexible, but these have been outlawed in recent times as they have been found to cause mutations in the aquatic environment - basically, they mimic oestrogen and can cause male fish to turn female! :wooha:

These are liquids and can migrate out of the PVC, causing ABS plastic to soften and distort - this is in addition to any heat issues caused by the cables.

These have been replaced with chemicals such as DINCH (Di Iso Nonyl Cyclohexane carbxylic acid ester) that don't affect aquatic life.

[/Science bit]

 

[rkauer]

Will rob this thread to inform fellow retro-computer users.

Thank you Plazma!

 

[TommyIII]

Yes, I just found this out a few days ago. It was mentioned in a feebay items descprption that had these same marks.
Searching google for pictures of this same item showed others with the same exact marks!
This thread helped me to fully understand the science behind it. Thanks.

I will make it a habit t wrap cords off to the side of the item when storing. Don't pull zip ties too tight on cords or a similar effect will happen to them too.

 

[BluesBrothers]

I think the worst i ever saw was to a Dragon 32 controller were the cable had completely made it's way through the case leaving a nasty hole. Boy did those guys get it wrong. Guess they dont like fish in Wales:shrug:

 

[SkydivinGirl]

I've had this happen with cheap material that you put on shelves to keep items from slipping. Not a pleasant experience picking up an item only to see little squares melted all over the bottom of the item you didn't want to slide off the shelf. My other recent experience with this was a set of jumper wires for breadboard use. I had the wires and breadboard in the same container and now the breadboard has a bunch of these little melting points.

Heather

 

[demolition]

So will heat/cold have any influence on this issue? I assume that as with other chemical reactions, heat will accelerate the process?

 

[rkauer]

Pretty much, yes. Heat always accelerates chemical reactions.

 

[roy_bates]

#waits for merlin to mention where heat isent part of the equation in a chemical reaction in melted plastics#:blased:...


anyway,not changing the subject or anything(ok,i am),has anyone thought about removing rust from old equipment using...electrolysis? .
it must be getting late,im starting to think

 

[rkauer]

Most known backward reaction to remove rust is a "bit" (no, not just a "bit") dangerous: you must blow overheated hydrogen over the rusted heated part. The hydrogen will capture the oxygen and react with it making water that evaporates almost instantly.

Problems:

#1: it IS dangerous because hydrogen + oxygen will react quite violently;

#2: you'll find that is really hard to buy hydrogen gas;

#3: the police/national security agency will schedule a very boring interview with you.

#4: you might want to know your grandchildren after that interview if your family permits.

---------- Post added at 23:26 ---------- Previous post was at 23:23 ----------

Now the serious part (not the above wasn't!): just get a place that can sandblast the metal to remove the rust then paint or chrome/electroplates a protective metal over it again.

 

[Merlin]

@ Roy

Your options are:-

1. Tannic Acid - this will convert the rust to ferrotannins and is the basis of the rust converter products that turn rust black and prime at the same time. These are basically an acrylic emulsion with tannic acid in there. They turn Iron (III) into Iron (II)

2. Hydrochloric or Hydrofluoric acid with an acid pickling inhibitor in it. These are used to clean off oxides from welds, particularly on stainless steels and they can also remove rust. They will also remove any plating on the parts.

3. Zinc Rich Cold Galvanising Spray - these contain zinc and try to emulate zinc plating on parts, as zinc is a sacrificial anode in a steel/zinc galvanic interface.These will stop any further rust from occurring.

I'd sand off the worst of the rust and go with 3) as the best option. Overcoat it with a Chrome spray if you want a more original look to the parts if they were tin plated.

 

[roy_bates]

some really good options there lads.


but,what was wrong with electrolysis? if a sacrificial plate is used and something like a 10+ amp power supply submerged in water.to remove the rust.
or something to that effect.
yeah,i couldn't get it out of my head.

 

[dougal]

That is something i never knew. I always thought it was caused by a soldering iron.

I've got a 1541 and loads of datasettes and a pc engine all with those markings.

 

[SteveDay]

I always use Naval Jelly/Phosphoric Acid to remove rust from iron based metals. It will quickly remove galvanized zinc plating too - which may or may not be of use.

 

[rootboy]

A friend at work is a Honda bike enthusiast. He's plating his old Honda bolts with zinc using a cheap programmable voltage/current converter that I found him on otherbay. He's happy as a clam with it. Granted, that doesn't get rid of the rust, he has to do that first. And it introduces hydrogen into the metal (he's been warned), which is a really bad thing.