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Other Stuff => Workbench => Topic started by: Vermis on July 29, 2014, 03:09:53 PM

Title: White metal corrosion - or not?
Post by: Vermis on July 29, 2014, 03:09:53 PM
I discovered some models that I'd left to soak in watery dettol about a couple of years ago. The dettol had evaporated a bit and gone sludgy, and there were some peculiar white blobs on some of the parts. When I scrubbed the blobs off there were some neat holes eaten into the metal, with what I assume was further corrosion in and around them. I scraped out the white/grey powdery stuff in them, and put the through a couple of sonic baths, soaks in fairy power spray, and good old-fashioned toothbrush scrubs.

The holes I'm not so worried about, and the parts have been etched (I guess) fairly matt grey, which I can live with; but there's still patches of white discoloration over the surface of some of them. It won't buzz or scrub off, but when it's scraped with a knife it comes off as a powdery residue, a lot like the stuff scraped out of the holes. Thing is, it's also a lot like the way primer turns powdery and scrapes off (or doesn't) after soaking in stripper, except I didn't prime any of the parts white!

I'm worried that it sounds a bit like lead rot, but IIRC GW got rid of lead by the time this titan went into production, and by the time I got into wargaming. I also had old metal hormagaunt bits in the same sludge, that I think still had some lead in them, and that ended up with a lot of fine pitting, but they don't have the same white patches.

Any clue to what's going on? Should I try to get rid of this white before it eats through my minis, or can it be left in place and painted over? Here's a pic that shows it off to some extent. (Click for a slightly closer look) The gun arm shows a few swiss-cheese-bulletholes from the corrosion, but doesn't have much white left on it. The flat plate has a lot more white discoloration - only a couple of tiny, minor patches of that white in the pic are due to glare.

(https://farm6.staticflickr.com/5588/14589880390_027237f4fc_o.jpg) (https://flic.kr/p/oefX8U)
Title: Re: White metal corrosion - or not?
Post by: von Lucky on July 29, 2014, 11:09:17 PM
No idea; maybe the Dettol bleached the colour so that it turned white?
Title: Re: White metal corrosion - or not?
Post by: Daeothar on July 30, 2014, 06:15:41 PM
Sounds and looks like there was some reaction between the chemicals you soaked the lot in and some components in the alloy.

Or... The fluid enabled an electrochemical reaction between the two types of metal you soaked. You say the Hormagaunt parts also had some evidence of pitting, right?

Who's to say what elements were used in the different alloys? I'd say it's certainly possible...
Title: Re: White metal corrosion - or not?
Post by: Vermis on July 31, 2014, 12:33:04 AM
Ta guys. I've had a look around, found out that tin pest (http://en.wikipedia.org/wiki/Tin_pest) is a thing and felt the hairs on my neck stand up. Good thing it only acts on unalloyed tin in extremes of temperatures. ;D I also stumbled across some examples of similar white-crust effects on tin and zinc objects, and a few suggestions to clear it off with mild acid. (vinegar, lemon juice) So I might test that on a small piece.

Though otherwise, I've calmed down a bit. I don't think me warlord titan's going to crumble to dust anytime soon. :)