[Healeys] Aluminum Brake & Clutch Cylinders

Andy Thorp bce257 at yahoo.co.nz
Thu Mar 6 13:38:17 MST 2014


This is the confusion and probably where the anodised myth started.

Chrome 6 is another term for hexavalent chrome or chromic acid.  Alodine or
Iridite are brand names for chromate conversion which is a passivation dip or
spray applied to aluminium parts to prevent surface corrosion. Mandatory in
aviation repair and an important first step when painting Healey shrouds.

It is not and never has been a form of anodising as there is no electricity
involved in the process, nor is it applied to the cylinder bores any more than
the entire cylinder body. Chromate has no scratch resistance at all so serves
no purpose for improving wear resistance.

Hexavalent chrome is so poisonous there are movies about it. That is why
trivalent chrome or phosphate coatings are now used instead, hence the EU
reference on the Girling website.

A simple check of the myth is to test the conductivity of an unworn part of
the cylinder bore with a multimeter. Chromated surfaces conduct electricity,
anodised surfaces do not unless they are scratched.

Andy.


--------------------------------------------
On Fri, 7/3/14, Wilko2 <e-wilkins at cox.net> wrote:

 Subject: Re: [Healeys] Aluminum Brake & Clutch Cylinders
 To:
 Cc: healeys at autox.team.net
 Received: Friday, 7 March, 2014, 8:32 AM

 They were originally, and are
 currently (pun intended) anodized. The latest
 form is the "chrome 6" as I referenced earlier. Chrome 6 is
 a type of
 anodizing.


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