Just for reference in case anyone else has a similar problem:
I contacted the manufacturer of Iridite, MacDermid. They do a kit called ARP 90 which consists of a pair of liquids which when combined give a chemical test of the presence of a protective layer, or not.
You try the test on bare...
Our aluminium parts are specified as being coated with Iridite NCP, which is clear (colourless). The older Alochrom 1200 coating was easy to see as it was yellow.
Of course one should use a trusted supplier who does what the drawing says, but is there a way to check it? Our purchasing guy just...
