BS EN ISO 10309:2016 pdf download – Metallic coatings — Porosity tests — Ferroxyl test
1 Scope
This International Standard specifies a method of re-vealing pores or other discontinuities,when testingmetallic coatings,that are not visibly affected by ferricyanide and chloride ions during the test periodand that are cathodic to iron and steel. This method
is especially useful for thick, hard chromium coatingsused for wear resistance.
NOTE 1With some coating materials a very thin layer isdissolved by the sodium chloride solution during a 10 min-ute application period (see 5.2.3). The impact of such dissolution is that potential porosity, i.e. pores that have beencovered over by very thin layers, are sometimes re-exposed.
Experience has shown that such potential porosity is fre-quently re-exposed during actual service.
2Normative reference
The following standard contains provisions which,through reference in this text,constitute provisionsof this International Standard. At the time of publi-cation,the edition indicated was valid. All standardsare subject to revision,and parties to agreementsbased on this International Standard are encouragedto investigate the possibility of applying the most re-cent edition of the standard indicated below. Mem-bers of IEC and lSo maintain registers of currentlyvalid International Standards.
lso 3696:1987,Water for analytical laboratory use —Specification and test methods.
Base metal ions, formed in corrosion cells at the bottom of discontinuities in metallic coatings migrate totreated test paper held in contact with the coatingsurface.The base metal ions retained on the treatedtest paper form a blue-coloured marking or spot whenthe treated paper is subsequently immersed in a sol-ution of a ferricyanide indicator solution.
4Reagents and materials
All chemicals used shall be of a recognized analyticalreagent grade and the water used shall be distilled ordeionized having a conductivity not greater than20 uS/cm (see lSo 3696).
4.2Preparation of the indicator solution
4.2.1Sodium chloride reagent
Dissolve 50 g of sodium chloride and 1 g of a non-ionic wetting agent in 1 litre of hot (90 c) water.Dissolve 50 g of gelatin or agar in the above men-tioned hot sodium chloride solution to provide gellingproperties.The solution will then gel upon cooling, butcan be re-liquefied, for use, by heating it to 35℃.NOTE 2 variety of non-ionic wetting agents is com-mercially available.
4.2.2Ferricyanide reagent
Dissolve 10 g of potassium hexacyanoferrate(ll) (pot-assium ferricyanide) in 1 litre of water. Measure thepH of the solution. If it is outside the range 6士0,2discard the solution and the reagent and obtain apurer grade of reagent.
4.3Optional equipment flat,flexible plastic sheet (template) with a squareopening, at least 10 mm x 10 mm in size,may beused to define the test area of the test paper after theappearance of the blue coloration (development).
5.1 Specimen preparation Clean and degrease the surface area to be tested us-ing a suitable solvent, such as 1,1.1 trichloroethane. 5.2Treated test paper
5.2.1lron contamination The paper used to prepare the test strips must be freeof any iron contamination.This may be verified by firstimmersing the paper in sodium chloride solution,blotting, and then immersing the paper in the potass-ium hexacyanoferrate(ll) solution. lron contaminationwill be evidenced by blue markings or spots,or aslight change or reduction in the white appearance ofthe dried paper when compared with the untreatedpaper.
5.2.2 Preparation lmmerse strips of a suitable paper, for example “wetstrength” filter paper,in the sodium chloride orsodium chloride-gelatin solution (see 4.2.1) until theyhave been thoroughly wetted by the solution. Re-move the strips and allow any excess solution to drainfor about 1 min. NOTES 3A clean glass plate has been found useful for drainingand holding the moistened test papers. 4Application of the sodium chloride solution directly to thetest surface produces diffuse rather than sharply definedpore sites. Therefore, the use of test paper which producessharply defined pore sites is recommended.
5.2.3 Applying the test paper Apply the wet test paper to the cleaned surface of thecoating pressing it firmly into contact. lt is essentialthat complete contact be made by the moistened testpaper over the entire area under test in order that thesodium chloride solution may react with any exposed