This International Standard specifies methods of assessing the quality of sealed anodic oxidation coatings on aluminium and its alloys by measurement of the loss of mass after immersion in phosphoric acid/chromic acid solution. This International Standard consists of the following two methods. - Method 1: assessment of quality of sealed anodic oxidation coatings by measurement of the loss of mass after immersion in phosphoric acid/chromic acid solution, without prior acid treatment. - Method 2: assessment of quality of sealed anodic oxidation coatings by measurement of the loss of mass after immersion in phosphoric acid/chromic acid solution with prior acid treatment. Method 1 is applicable to anodic oxidation coatings intended for decorative or protective purposes or where resistance to staining is important. Method 2 is applicable to anodic oxidation coatings intended for architectural purposes. For less severe applications, Method 1 may be more suitable. The methods are not applicable to the following: - hard-type anodic oxidation coatings which normally are not sealed; - anodic oxidation coatings that have been sealed only in dichromate solutions; - anodic oxidation coatings produced in chromic acid solutions; - anodic oxidation coatings that have undergone a treatment to render them hydrophobic. NOTE The methods are destructive and can serve as reference methods in case of doubt or dispute regarding the results of the test for loss of absorptive power (see ISO 2143[1]), or the measurement of admittance (ISO 2931[2]).