ISO 9717:2010 pdf free download – Metallic and other inorganic coatings一 Phosphate conversion coating of metals.
6.3.1 Rinsing
After phosphating, thorough rinsing with water is necessary in order to remove soluble salts which would otherwise tend to promote blistering under organic coatings. Parts, especially those with crevices, folds, or seams, as well as those treated with the accelerated phosphating process, shall be rinsed as follows:
a) After treatment by an accelerated process, items are rinsed thoroughly, first in flowing cold water and then in hot water at a minimum temperature of 75 °C, and finally washed in the hot dilute °chromic solution described below. The accumulation of treatment chemicals in the rinse waters is avoided by maintaining a sufficient flow of cold water and by periodic renewal of hot water. The acidity of the hot water shall not be allowed to exceed that corresponding to 0,75 ml of 0,4 % (mass fraction) sodium hydroxide solution when tested by a suitably calibrated pH meter or by any other appropriate method.
Alternative processes to the chromic rinse such as those based on silane acid systems may be used provided that the efficiency and appropriate control of the process can be confirmed.
b) After treatment by an unaccelerated process, items are rinsed in flowing cold water, then in either hot water (65 °C minimum) or the hot dilute chromic solution (65 °C minimum).
The chromic” wash solution normally consists of the range of 15 g to 50 g of chromic acid, or of alkali metal chromate or alkali metal dichromate, or of a mixture containing approximately equal parts of chromic and phosphoric acids, per 100 litres of water. A higher concentration than the maximum quoted above is not to be used on surfaces which will be in contact with, or in proximity to, hazardous substances. In other cases, higher concentrations of chromic acid, chromate or dichromate may be used up to a maximum of 500 g per 100 litres of water, where such concentrations will give overall beneficial results and where the effect of local enrichment or drainage will not be detrimental under organic-based systems.
WARNING — The repeated handling with bare hands of items that have been given a “chromic” wash may constitute a health hazard.
c) The wash waters, hot or cold, used for unaccelerated and accelerated processes shall not contain chloride, calculated as chloride ion, in excess of 0,5 g/l. when determined by the method described in Annex B.
6.3.2 Staining
Parts that are to be stained by water soluble pigment are dyed at this stage [see 4.1 j)J. Staining by spirit dye
is dyed after drying.
6.3.3 Drying
Parts are dried after thorough rinsing. Forced drying is also used, especially for those with crevices, seams, etc.
6.3.4 Identification of type of phosphate conversion coating
Details of the procedures of identification of types of phosphate conversion coatings are described in Annex C.
6.4 Thickness of coating
The coating mass, rather than thickness, is measured in accordance with ISO 3892 and shall be determined on an item after treatment by phosphating, washing, and drying and before any heat treatment and sealing (see 5.4).
For quality assurance purposes, instruments which are available and which give a direct reading of coating mass per unit area may be used. It is, however, essential that they are calibrated against standard coatings having a coating mass per unit area of the same order as those being inspected.