Carbon Steel Spring in ABS Plastic Assy Corrosion
Carbon Steel Spring in ABS Plastic Assy Corrosion
(OP)
We are seeing a Music Wire Spring ASTM A228 exhibiting rust very quickly during cycle testing. The spring is enclosed in an ABS housing. Small fines of ABS are present from wear. The spring when cycled by itself in ambient conditions, exhibits little or no rust. What is the Chemical reaction taking place that is causing ABS to rust carbon?





RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
If there is no obvious environmental corrodent, then maybe the ABS moisture content was sufficient to produce corrosion. This doesn't seem likely.
Perhaps there is an additive to the ABS that promoted the corrosion. Contact the ABS supplier and ask them about flame retardants, UV stabilizers, heat stabilizers, melt flow rate modifiers, etc.
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
I made the suggestions above to our molding people and thay are telling me there aren't any UV stabilizers, Fire retardants, or melt flow rate modifiers. I am NOT a chemical engineer or plastics engineer, but somehting in there is causing all this oxidation. The parts are molded in a very dry arid area of the country, so trapped humidity isn't a problem.. Does ABS have a curing time, or a time it should wait before being used?
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
Are your molding people intimately familiar with the ABS material and its production method? Additives to plastics are very common. You can conduct fourier transform infrared spectrometry (FTIR) on the ABS to identify constituents, which may help identify a possible corrodent.
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
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Plymouth Tube
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
You are using an extremely limited definition of hydrogen embrittlement. The corrosion process generates hydrogen, which can enter the steel and weaken it. You can't say that the parts fail before corrosion is a problem - your parts are covered in rust, which could result in hydrogen assisted cracking (pick your acronym: HE, HASC, HISC, etc.), or fatigue initiation from a corrosion pit in less time than if the fatigue initiated from the wire surface. If you haven't looked at the spring surfaces with an electron microscope, you should.
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion
What is the hardness of your spring?
If you have some ready to install parts on the shelf you might want to do a magnetic particle test on them. If these are not already cracked you might be able to reclaim them by a bakeout.
Ask your lab if they can clean the fracture surface and look for fatigue striations.
RE: Carbon Steel Spring in ABS Plastic Assy Corrosion