BS EN ISO 8407-2021 pdf free download – Corrosion of metals and alloys — Removal of corrosion products from corrosion test specimens.
2 Normative references
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3 Terms and definitions
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4 Procedures
4.1 General
4.1.1 A light mechanical cleaning treatment by brushing, e.g. a soft bristle brush under running water,should first be applied to remove lightly adherent or bulky corrosion products.
4.1.2 If the treatment described in 4.1.1 does not remove all corrosion products, it will be necessary to use other procedures. These are of three types:
a) chemical;
b) electrolytic;
c) more vigorous mechanical treatments.
NOTE These treatments will also remove some base metal.
Whichever method is used, it might be necessary to repeat the cleaning treatment to ensure completeremoval of the corrosion products.Removal shall be confirmed by visual examination.The use of a low-power microscope (i.e.x 7 to x 30) is particularly helpful with a pitted surface since corrosion productscan accumulate in pits.
4.1.3 An ideal procedure should remove corrosion products and not result in the removal of anybase metal. Two procedures can be used to confirm this point.One procedure uses a control specimen(see 4.1.4) and the other requires a certain number of cleaning cycles on the corroded specimen (see4.1.5). The procedures shall be maintained while the rust removal performance of the solutions listed inTables A.1 and A.2 is not impaired.
NOTE1 Indications that the solution needs to be discarded can be discoloration or the presence of a significantamount of corrosion products in the solution.
NOTE2 Some solutions might need some aging before working without etching the substrate.
4.1.4 Uncorroded control specimens,which should be similar chemically，metallurgically andgeometrically to the test specimens,should be cleaned by the same procedure as used for the testspecimen. By weighing the control specimen before and after cleaning (weighing to the fifth significantfigure is suggested, e.g. a 70 g specimen should be weighed to three decimal places), the metal lossresulting from cleaning may be determined.The mass loss of the control specimen will reflect the massloss of test specimens resulting from the cleaning procedure.
4.1.5 The cleaning of each corroded test specimen should be repeated several times after the removalof the corrosion products is completed. The mass shall be plotted as a function of the periods ofcleaning cycles with the same interval time or time units (see Figure 1).Point A represents the mass ofcorroded specimens before the start of the cleaning. In many cases, two straight lines,AB and BC, willbe obtained. Line AB characterizes the removal of corrosion products and may not always be visible.Line BC characterizes the removal of the substrate after the corrosion products are completely removed.Point D, which characterizes the mass of the pure metal at zero number of cleaning cycles, is obtained byextrapolation of line BC to the ordinate axis. In some cases, the relationship may not be linear, and themost appropriate extrapolation shall then be made. If the relationship of B and C is not linear, a linearregression method, e.g.by applying the least squares from later points of cleaning cycles, can be used forestimation of the point for the D value.
lf the durations of each cleaning step are not equal, the x-axis should be expressed in units of cumulativeexposure time in the cleaning solution, rather than the number of cleaning steps used up to that point.BS EN ISO 8407 pdf download.