Any idea what caused this corrosion? - Page 1
Forum section: electronics / repair

author: Axtman
author_rank: Regular Contributor
timestamp: April 25, 2023, 10:51:08 pm
content: I have worked on a LOT of guitar amplifiers. A Gallien Kruger Backline 210 amplifier chasis was given to me for free. The PC board and internals looks pristine with no signs of corrosion, but the jacks are terribly corroded.I figured that either 1) the plastic off-gassed and corroded the metal parts or 2) someone tried to clean the jacks with a cleaner that was not plastic safe.Have you ever seen this before?

author: abdulbadii
author_rank: Frequent Contributor
timestamp: April 26, 2023, 12:47:56 am
content: only cheat chatgpt with some rephrases of mine, the causes:- Localized corrosion: Certain environmental conditions can lead to localized corrosion, such as pitting or crevice corrosion, where small areas of the metal surface are corroded at an accelerated rate. This can occur in areas where there are local differences in the environment, such as in crevices, gaps, or areas with stagnant electrolytes, leading to rapid corrosion in those specific locations.- Presence of corrosive substances: If the ambient environment contains corrosive substances such as acids, salts, or other chemicals, they can react with the metal surface and accelerate the corrosion process. These substances can increase the rate of metal dissolution or create a corrosive environment that promotes the breakdown of the metal's protective oxide layer, leaving the metal surface vulnerable to further corrosion.- High humidity or moisture: Moisture can facilitate the electrochemical reactions involved in corrosion. When a metal is exposed to high humidity or moisture, it can create an electrolyte that enhances the flow of electrons between the metal surface and its environment, leading to accelerated corrosion.- Dissimilar metal contact: When two or more dissimilar metals come into contact in the presence of an electrolyte, such as in the presence of moisture, an electrochemical reaction can occur, leading to accelerated corrosion of one of the metals. This is known as galvanic corrosion, and it can result in rapid corrosion of the more reactive metal.- Temperature: High temperatures can increase the rate of corrosion by providing the energy required for chemical reactions to occur more rapidly. Elevated temperatures can also cause changes in the microstructure of the metal, weakening its corrosion resistance and making it more susceptible to corrosion.- Lack of protective coatings/inhibitors

author: james_s
author_rank: Super Contributor
timestamp: April 26, 2023, 06:14:30 am
content: Possibly salt air from a marine environment but I think that's unlikely given the condition of everything else. I'd guess it is a manufacturing defect, maybe acid used in the plating process wasn't washed off properly.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: April 26, 2023, 06:42:42 am
content: I saw similar unusual corrosion on a Gallien Krueger (though not nearly as bad), so it is probably Gallien Krueger specific.So probably either a dodgy manufactured batch of connectors, or some assembly issue at the factory.Edit: The one I had was a MB150S III, a completely different model to yours, so I'm not sure what that might suggest really.But all 4 jack sockets were corroded and had to be replaced.Most unusual.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: April 26, 2023, 08:45:13 am
content: Nasty. Was it water wicking along and down and into the jack plugs - so the plating on the jack plugs corroded? Being a white powdery deposit suggests some sort of salt or hydroxide, rather than having a greenish tinge which suggests oxides of copper or chrome.

author: Haenk
author_rank: Super Contributor
timestamp: April 26, 2023, 09:19:56 am
content: I would assume someone used some "contact cleaner", which is why it is limited to the plugs only.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 26, 2023, 10:56:38 am
content: The top picture looks like it may be whiskers from pure tin or zinc plating. See attachment from NASA publication. Certainly the weather the Seattle might contribute. Do you know anyone with a microscope?

author: RoGeorge
author_rank: Super Contributor
timestamp: April 26, 2023, 11:27:40 am
content: Quote from: Axtman on April 25, 2023, 10:51:08 pmI've noticed something similar (maybe less pronounced) at a radio, after returning from a vacation at the beach, on the seaside shore. Only after returning home, weeks/months later, some metallic parts (not all of them, only certain metals) developed a whitish "salt-like" cover (not sea-salt), some white oxide/salt/rust/corrosion don't know how to call it.During the vacation month in the salty air, it was all OK. Only after coming back home, the whitish thing started to grow.

author: tszaboo
author_rank: Super Contributor
timestamp: April 26, 2023, 11:52:22 am
content: Quote from: Haenk on April 26, 2023, 09:19:56 amI know a technician, who swears that the break cleaner used for cars is the best thing ever to clean connectors.I gave up trying to explain him, that's really a hill he is ready to die on.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: April 26, 2023, 12:02:56 pm
content: Quote from: jpanhalt on April 26, 2023, 10:56:38 amBoth Tin and Zinc oxides are a white powder. I now remember seeing the same crusty-dust on the interior metalwork of old valve radios and televisions left neglected in sheds.

author: Psi
author_rank: Super Contributor
timestamp: April 26, 2023, 12:10:19 pm
content: It could have been very close to a fog machine.A lot of that is just water vapor and isn't something people consider to be "getting the device wet".The water corrodes things and the glycerin makes the device sticky so dust gets stuck to it.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 26, 2023, 12:11:39 pm
content: "Brake cleaner" can be almost any organic solvent or mixture thereof. It used to be TCE (trichloroethylene) and/or tetrachloroethylene (PERC) alone or in mixture. Today, to meet VOC and other requirements, it may be mostly CO2 and acetone. Liquid CO2 is an excellent solvent. History: Before modern HPLC became commonplace, Alsoph Corwin was doing research (funded by Perkin Elmer as I recall) using relatively low-pressure, closed-column chromatography with CO2 as the mobile phase.Example 1:http://docs.crcindustries.com/msds/5151.pdf(mostly acetone)Example 2:http://www1.mscdirect.com/MSDS/MSDS00014/02982908-20121023.PDF(PERC and TCE)Example 1 is often labeled "chlorine free" or words to that effect. I prefer a mixture of chlorinated hydrocarbons (as in Example 2).EDIT: @AB Do we know whether that "corrosion" is oxides or whiskers? Hence, my suggestion to use a microscope. It could also be both.

author: paul@yahrprobert.com
author_rank: Regular Contributor
timestamp: May 04, 2023, 09:20:29 pm
content: You mentioned outgassing. I've seen something similar on plastic parts which I think was due to the plasticizer coming out of the part and reacting with something (oxygen, water, ??) in the air. There are many plasticizers dissolved in plastics to make them more supple. BPA used to be a big one, and I wouldn't be surprised if some replacements might be a little sketchy. Any chemists here?