Re: Master Blaster (was: What car is the best buy?)

["Fred Munro" <munrof@isys.ca>]

Gary;

    The sandblast grit I use is manufactured by Fisher-Wavy, a local
aggregate supplier. They make it in white (~60 grit) and in black (20/40
grit). I have been using the white -  this gives a finely mottled surface
which provides excellent adhesion for primer. Heavily rusted and pitted
surfaces may require heavy priming or filling to fill in the rust pits, but
the surface generated by the sand itself is easily filled by the primer.

    As to electroplating zinc, I have come across a method which could be
used on an auto panel in one of my more arcane reference sets ( The Chemical
Formulary, published in the early 1940's - it tells you how to formulate
almost anything) . The method is called "Brush Electroplating" and it is
probably the basis for the electroplating brushes we have discussed
previously.
    To plate zinc with this method, a cloth is saturated in plating solution
and wrapped around a zinc rod or bar. The zinc rod is connected to the
positive terminal of a battery and the metal to be plated is attached to the
negative terminal. The surface to be plated is cleaned. The wet cloth is
then rubbed continuously across the metal surface and zinc is plated on to
the metal. Voltages of 1.5 - 6 volts are required. The advantage of this
method is that only a small quantities of plating solution is required. The
disadvantage is that only a thin deposit can be made, but the plated
appearance is said to be excellent ( not that it matters under paint).
    Now to the major disadvantage. Almost all plating solutions are cyanide
based, and this is the primary reason disposal of spent plating solutions is
such a problem. For example, the Formulary lists a zinc plating solution
composed of zinc cyanide, sodium cyanide, and sodium hydroxide. Cyanide
compounds are particularily deadly ( gas chamber, anyone?) and must be
handled with extreme care. I definitely would not recommend playing around
with this stuff just to get a bit of zinc back on an Audi fender!
Alternative plating solutions may be available, but I haven't come across
the formulations yet.


Fred Munro
'91 200q  258k km

-----Original Message-----
From: Steinbru@VNET.IBM.COM <Steinbru@VNET.IBM.COM>
To: FRED MUNRO <munrof@isys.ca>
Cc: dougq@iglou.com <dougq@iglou.com>; bryan@umr.edu <bryan@umr.edu>;
eyvind.spangen@ha-nett.no <eyvind.spangen@ha-nett.no>; rmruss@pangea.ca
<rmruss@pangea.ca>
Date: Friday, September 18, 1998 12:04 AM
Subject: Master Blaster (was: What car is the best buy?)


>Ref:  Your note of Thu, 17 Sep 1998 22:18:17 -0400
>
>Fred,
>Is there a product or brand name for the grit?  Seven bux is as
>cheap as "playground sand".  I have NOT searched far and wide,
>and am not particularly bothered by excessive dust (work outdoors
>on this kind of stuff), but welcome hints for getting a better
>"primer ready" surface.  My usual result needs "red lead" or
>other surface prep plus primer, so any thing that gets directly
>to a primer ready surface is welcome.
>
>Yes, I think I have seen the "electro-plating" stuff a little
>more recently than that; but now that you mention it, death at
>the hands of "product liability" would be likely for such stuff.
>Most metallic salts are toxic and probably some acid would have
>been part of the mix as well.  The brush should have only been
>required to hold and distribute the electrolyte I would imagine.
>Also, I'm not sure any type of cynaide would be necessary.  I
>only recall the use of that for separating certain precious
>metals from ore --not for electo-plating, but then it's been
>awhile since I delved into that stuff.  Cadmium plating was
>popular at one time, but particularly noxious.
>
>Wonder what one could "kit up" on their own?  Any thoughts?  A
>cheap and easy galvanize prep would certainly be of general
>interest to our group!  This is getting to be an interesting
>aside, post the entire thread to the list with your answer if
>you like.
>--Gary
>
>--REFERENCE----------------------------------------------------------------
----
>From: "Fred Munro" <munrof@isys.ca>
>To: <Steinbru@VNET.IBM.COM>, <dougq@iglou.com>,
>    <eyvind.spangen@ha-nett.no>, <rmruss@pangea.ca>
>Cc: <bryan@umr.edu>, <steinbru@juno.com>
>Subject: Re: What car is the best buy?
>Date: Thu, 17 Sep 1998 22:18:17 -0400
>
>Gary;
>
>    I use an 80 grit white abrasive designed for sandblasting. It cuts
>quickly and produces no dust - just lots of sand particles bouncing around.
>It costs around $7 for a 100lb bag. I used to use screened sand from a
local
>sand pit (hey, it was free), but the dusting was unbelievable. The 80 grit
>sand leaves a good mechanical key on the metal surface for primer adhesion.
>    I remember seeing adds for the electroplating brush you mention in old
>copies of Popular Mechanics from the '50s & '60s. It supposedly replated
>chrome on bumpers. Might work if the brush bristles were chrome, the
>solution was a chrome salt dissolved in water, & it was hooked up to a 12v
>car battery. Might work - but I note they are no longer advertised. Of
>course, that might have something to do with the fact that the plating
>solution must contain sodium cyanide if you want a smooth, shiny plate.....
>
>Fred
>-----Original Message-----
>From: Steinbru@VNET.IBM.COM <Steinbru@VNET.IBM.COM>
>To: FRED MUNRO <munrof@isys.ca>; dougq@iglou.com <dougq@iglou.com>;
>eyvind.spangen@ha-nett.no <eyvind.spangen@ha-nett.no>; rmruss@pangea.ca
><rmruss@pangea.ca>
>Cc: bryan@umr.edu <bryan@umr.edu>; steinbru@juno.com <steinbru@juno.com>
>Date: Tuesday, September 15, 1998 12:19 PM
>Subject: What car is the best buy?
>
>
>>Fred.
>>I had the same setup before theft, now I just siphon out of the bag.
>>What abrasive material do you use.  I have used everything from white
>>silica sand to regular mason's sand (sharp edges).  The former pits the
>>metal surface a little more than would seem to be good for auto paint,
>>the latter MUCH more.  What works best for you?
>>
>>I am interested if there is anyway to put zinc on electrolytically
>>for small repairs?  I recall some ancient ads whereby metals could
>>be plated with an "electric brush" and some special solutions?  Is
>>that just science fiction?
>>--Gary
>>
>>ps, I'm thinking to try one of my 2.5 gal paint pots as a "make do"
>>pressure blaster, I'll let you know --they are under $100.
>>--REFERENCE---------------------------------------------------------------
-
>----
>>Date: Mon, 14 Sep 1998 20:51:35 -0400
>>From: "Fred Munro" <munrof@isys.ca>
>>Subject: Re: What car is the best buy?
>>
>>Jeff;
>>
>>    I use a 100 lb capacity siphon feed sandblaster I bought at Sears for
>>$70 many years ago. It works fine for spot repair and small areas(~1
square
>>foot) - anything larger takes a long time and lots of sand. Pressure
>>blasters use less sand and are more efficient, but they cost around $400 -
>>Princess Auto carries pressure blasters in Winnepeg.
>>    Sandblasting is the most effective way to completely remove rust and
it
>>leaves an excellent surface on the metal for mechanical paint adhesion.
You
>>can grind away the rust with an abrasive disc, but this removes too much
>>good metal and can leave the panel thin, weak, and prone to buckling in
>that
>>spot. It also tends to leave small pockets of rust intact at the bottom of
>>the pits. Sandblasting completely removes the soft rust and leaves the
>>harder good metal intact ( it also does a nice job of raising grain on
wood
>>if you are into artsy woodworking, but that's another story ...). It
leaves
>>the metal surface mechanically and chemically clean, and the metal will
>>immediately start rusting, so treatment with the acid metalprep is a
>>requirement for a lasting repair.
>>
>>HTH
>>
>>Fred Munro
>>'91 200q  257k km
>>- -----Original Message-----
>>From: Ron Mruss <rmruss@pangea.ca>
>>To: 'Fred Munro' <munrof@isys.ca>
>>Date: Sunday, September 13, 1998 12:34 PM
>>Subject: RE: What car is the best buy?
>>
>>
>>Fred,
>>
>>Thanks for the info.  I think that the joints on the passenger side rear
>>wheel well are rusting just as you described.  I'm kind of appaled at the
>>repair job that the bodyshop did.  It looked great on the surface, but
look
>>a little deeper and...not so great.  Oh well.
>>
>>All this is new to me so forgive this next question:  is a sandblaster
>>suitable for bodywork expensive?  I have access to a paint sprayer, but I
>>don't know anyone who has a sandblaster.
>>
>>Thanks again.
>>
>>Jeff
>>
>