[ausev] Paint question

[m. edmund howse]

I think this was actually the product.
http://www.therustdoctor.com/?OVRAW=rust%20converters&OVKEY=rust%20converter&OVMTC=standard&OVADID=7607665011&OVKWID=45611893511

marv



Chris Robison wrote:

>m. edmund howse wrote:
>  
>
>>Something I've used in the past on my 69 mustang turns the iron oxide 
>>into an iron chloride.  It's very simple to apply and is almost 
>>immediately paintable, but I've forgotten what it is. Then again I can 
>>probably find it if there is any interest.
>>
>>    
>>
>
>I don't know what will produce iron chloride as a coating, but dip a 
>rusty steel or iron part in hydrochloric acid and the rust will be 
>converted to iron chloride (ferric chloride) which is produced along 
>with water and gets dissolved in the acid. Continue to introduce rust to 
>the liquid, and I believe eventually you'll have nothing but ferric 
>chloride in an aqueous solution (no acid left). I imagine it would be 
>very similar to the nasty brown ferric chloride solution that you can 
>buy in bottles at Fry's for etching circuit boards.
>
>In general for rust treatment, the two usual chemicals are phosphoric 
>acid, and tannic acid.  Phosphoric acid leaves the metal with an iron 
>phosphate coating, and tannic acid (the same stuff in tea and coffee, 
>btw) creates a dark black iron tannate coating. By themselves, both 
>require the rust to function, and both (especially phosphoric acid) 
>should be thoroughly washed off after treatment, or they'll continue to 
>etch the metal. These coatings also do not constitute a robust 
>protection of the substrate and should be followed with something else 
>like primer and paint, powdercoat, etc.
>
>To make this easier, some modern products include a primer as part of 
>the formula. These seem to use primarily tannic acid instead of 
>phosphoric in general. I speculate this may be because it's less 
>reactive with the bare metal, so once the reaction is finished, it's not 
>as critical to remove all of it, and whatever's left behind just remains 
>in solution with the primer while it dries. At any rate, this is the 
>action that's happening when a product like Rust Reformer changes color 
>-- as the tannic acid changes the rust into iron tannate, the coating 
>changes from white to black. When it's dry, the metal is converted, 
>primed and ready to paint.
>
>Here's a page discussing tannic and phosphoric acid (and a bunch of 
>other stuff, mostly relating to cleaning and preservation of found items 
>from a saltwater environment):
>
>http://nautarch.tamu.edu/class/anth605/File10b.htm#Tannic
>
>
>   --chris
>
>
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>

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