A caution about the excellent Castrol purple cleaner
 

I bought this stuff because Grant and others said it worked well to
remove oils. And it sure does. I suspected that it might be pretty
strongly alkaline because of the soapy feel. And I got proof when
washing some anodized parts that came in for mods. The Castrol purple
stuff started to remove the dye (black) and on the machined surfaces
started to dull them slightly. I will still use the stuff on aluminum
if I need to but will not let it sit for long. I wonder if it would
make a good weld prep for aluminum?
ERS

A caution about the excellent Castrol purple cleaner
 

I used to clean and etch aluminum parts in a similar highly caustic
purple soap (Oakite?) as part of the Iridite process.

jw

A caution about the excellent Castrol purple cleaner
 

It does contain lye, Eric, in which aluminum is highly soluble ..

GWE

Eric R Snow wrote:
I bought this stuff because Grant and others said it worked well to
remove oils. And it sure does. I suspected that it might be pretty
strongly alkaline because of the soapy feel. And I got proof when
washing some anodized parts that came in for mods. The Castrol purple
stuff started to remove the dye (black) and on the machined surfaces
started to dull them slightly. I will still use the stuff on aluminum
if I need to but will not let it sit for long. I wonder if it would
make a good weld prep for aluminum?
ERS

A caution about the excellent Castrol purple cleaner
 

Eric R Snow wrote:

I bought this stuff because Grant and others said it worked well to
remove oils. And it sure does. I suspected that it might be pretty
strongly alkaline because of the soapy feel. And I got proof when
washing some anodized parts that came in for mods. The Castrol purple
stuff started to remove the dye (black) and on the machined surfaces
started to dull them slightly. I will still use the stuff on aluminum
if I need to but will not let it sit for long. I wonder if it would
make a good weld prep for aluminum?
ERS

I use the purple degreaser myself, in fact I have a 5 gal of it. It is
one of the few chemicals in my (home) shop that I use gloves when using.
It is very strongly alkaline (lye) and will do a number on your hands
just like cement will.

Pete C.

A caution about the excellent Castrol purple cleaner
 

It is so good that the CA air quality folks have banned the sale in
SoCal. I am now buying mine in AZ.

A caution about the excellent Castrol purple cleaner
 

On Fri, 18 Nov 2005 16:16:25 -0800, Grant Erwin
wrote:

It does contain lye, Eric, in which aluminum is highly soluble ..

Surely it's potassium hydroxide, not sodium hydroxide ? Nearly as much
saponification on grease, but a lot lighter on metals.

I'd still be cautious about using it around aluminium. One of the
popular bike cleaners (Muc-Off) contains KOH and is known to damage
Mavic rims. This says more about the problems with the anodising on
Mavic rims than the cleaner though! I'm keeping the cleaner, losing the
rims.

A caution about the excellent Castrol purple cleaner
 

Andy Dingley wrote:

On Fri, 18 Nov 2005 16:16:25 -0800, Grant Erwin
wrote:

It does contain lye, Eric, in which aluminum is highly soluble ..

Surely it's potassium hydroxide, not sodium hydroxide ? Nearly as much
saponification on grease, but a lot lighter on metals.

I'd still be cautious about using it around aluminium. One of the
popular bike cleaners (Muc-Off) contains KOH and is known to damage
Mavic rims. This says more about the problems with the anodising on
Mavic rims than the cleaner though! I'm keeping the cleaner, losing the
rims.

Nope, the label on the 5gal of Zep brand purple degreaser I have says
Sodium Hydroxide.

Pete C.

A caution about the excellent Castrol purple cleaner
 

On Fri, 18 Nov 2005 16:16:25 -0800, Grant Erwin
wrote:

It does contain lye, Eric, in which aluminum is highly soluble ..

GWE

Eric R Snow wrote:
I bought this stuff because Grant and others said it worked well to
remove oils. And it sure does. I suspected that it might be pretty
strongly alkaline because of the soapy feel. And I got proof when
washing some anodized parts that came in for mods. The Castrol purple
stuff started to remove the dye (black) and on the machined surfaces
started to dull them slightly. I will still use the stuff on aluminum
if I need to but will not let it sit for long. I wonder if it would
make a good weld prep for aluminum?
ERS
Well, there ya go.
ERS