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ISO 3210:2017 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 acid solution(s). It 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 a phosphoric acid based 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 a phosphoric acid based 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 outdoor architectural purposes. For less severe applications, Method 1 can 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 treatment to render them hydrophobic. NOTE 1 The methods assess the quality of hydrothermal sealing applied to anodized aluminium. They can be appropriate for other sealing methods. NOTE 2 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) or the measurement of admittance (see ISO 2931).