Plastic degradation near sea when assembled with metal part

[gao7857]

Hi, I noticed the plastics are likely to degrade easier/quicker near sea (or in sea water) when it is in contact with metals. I feel there are some electrochemical activities going on. Can anyone help me understand this phenomenon, and is there any literature discussing it?
Thanks!
The plastic is molded before assemble with the metal part.

 

[TVP]

What type of plastic? Does it have any reinforcing material (glass or carbon fiber) or other fillers (copper, etc.)? Have you investigated the possibility that the plastic is not suitable for direct exposure to ultraviolet radiation? Many plastics require a UV stabilizing additive to be used in continuous outdoor service, while some just are not suitable at all.

 

[btrueblood]

Nylon can undergo SCC if exposed to zinc chloride (from chloride corrosion of zinc-plated steel). That's one known combination where a type of degradation can occur due to metal/plastic interfaces. There are types of nylon which are resistant to the attack, and other plastic resins which are relatively immune.

 

[gao7857]

Btrueblood,
Yes nylon66 is one of our plastic parts that had this issue.
Which types of polyamide is resistant? pa12? because of how it is polymerized?
I assume fluoropolymers are immune to this mechanism?
Thanks.

 

[btrueblood]

Dunno, but I think it can be handled with additives to the polymer melt also. Google, my friend.