Re: alfa-digest V7 #1083

[KDHX@domain.elided]

To Jerry Wagley,
  Jerry, I've had some experience with rust and here's hopefully something 
that will help.  For small parts, immersion in phosphoric acid solution will 
eat away existing rust and convert it to hematite ,a stable compound.  This 
is referred to as rust conversion. The way I made this solution was to buy 
85% phosphoric acid by the quart from Fischer Scientific (who actually 
wouldn't sell it to me without a hazardous waste certificate-I had to go 
through a local distributor that they reccommended-cost about 25.00/qt of 
concentrate) and add to 5 gallons of water in a common drywall bucket.  Parts 
are immersed overnight depending upon the temperature and removed when a grey 
coating  (hematite) is seen forming where the rust once was.  Don't leave for 
excessive lengths of time as it will eat metal if left long enough. It is 
best to have all paint removed so that all the metal can be treated and 
stabilized.  This acid solution seems to have no effect on paint for a 24 
hour time period although I wouldn't risk a good finish doing this. This can 
even be used on large parts like doors.  You can remove the door , wrap in 
heavy plastic sheeting and duct tape securely.  Pour the acid solution into 
the door cavity using a funnel if neccessary and leave overnight as for small 
parts.  Be sure to wash thoroughly with hot water to neutralize the acid.  
The acid can be poured out of the plastic sheeting back into the plastic 
bucket and reused.  You will need help with this step.  Be sure to use heavy 
4mil or greater plastic to prevent accidental tear and major acid spill.  I 
rest large objects on cardboard when treating to cushion the plastic at 
pressure points.  5 gals of acid is quite heavy. I also left these large 
parts outside to prevent against a leak and a major mess. On large parts like 
fenders that are more difficult and awkward to handle I used oxisolv,  a 
product available from Eastwood Co.  It is brushed on and kept wet for 30 
minutes and then cleaned off with thinner or lacquer thinner.  It will remove 
the rust similar to phosphoric acid but has the advantage of leaving a zinc 
coating on the surface of the metal.  It's considerably more expensive than 
bulk acid though.  Be sure to keep the part wet and remove before it starts 
to dry or it will leave drip marks of zinc coating that can be seen through 
paint and need to be sanded off  (guess how I know this).  The next step is 
rust stabilizer such as damp proof red primer.  Rustoleum is not bad but 
corroless from Eastwood is better.  Be sure to test the next layers of paint 
for compatibility with whatever primer you chose.  Heavier more durable 
marine primers that are self mending to rock chips etc can be used in out of 
the way places like inside rockers, inside doors etc.  Most of what I've told 
you,  you will find in Tom Ducibella's book on restoring a 1969 Alfa Romeo 
Duetto.  This is available from AROC-New England Chapter.  You can also read 
about rust treatment in Eastwood's info section at their website, 
www.eastwoodco.com.  Also read the tech article at the St. Louis Club site, 
www.catenary.com/ar/welcome.html   

Tim Malaney 
St. Louis, Mo.
1967 Duetto
1964 Impala Convertible (No it doesn't hop)

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