ISO/TC 107/SC 7 - Corrosion tests

ISO 18332:2007 defines porosity and its associated terms, and outlines the principles involved in porosity testing of metallic and related inorganic coatings. The purpose of porosity testing is also considered, thereby assisting the user to select the most suitable test for the product and its service application. The porosity test cannot be used to establish corrosion-performance standards.

ISO 10308:2006 reviews published methods for revealing pores (see ISO 2080) and discontinuities in coatings of aluminium, anodized aluminium, brass, cadmium, chromium, cobalt, copper, gold, indium, lead, nickel, nickel-boron, nickel-cobalt, nickel-iron, nickel-phosphorus, palladium, platinum, vitreous or porcelain enamel, rhodium, silver, tin, tin-lead, tin-nickel, tin-zinc, zinc and chromate or phosphate conversion coatings (including associated organic films) on aluminium, beryllium-copper, brass, copper, iron, NiFeCo alloys, magnesium, nickel, nickel-boron, nickel-phosphorus, phosphor-bronze, silver, steel, tin-nickel and zinc alloy basis metal.

This part of ISO 4524 provides procedures for conducting mixed flowing gas (MFG) environmental tests involving exposures to controlled quantities of corrosive gas mixtures. It describes the required equipment and the methods for gas, temperature and humidity control that enable tests to be conducted in a reproducible manner. Reproducibility is measured through the use of control coupons the corrosion films of which are evaluated by mass gain, coulometry or by various electron and X-ray beam analysis techniques. Reproducibility can also be measured by in situ corrosion rate monitors using electrical resistance or mass frequency change methods. MFG tests can be used to: _ evaluate novel electrical contact metallization for susceptibility to degradation due to environmental exposure to the test corrosive gases; _ evaluate the shielding capability of connector housings that may act as a barrier to the ingress of corrosive gases; _ evaluate the susceptibility of other connector materials such as plastic housings to degradation from the test corrosive gases. MFG tests are not normally: _ used as porosity tests (for guidance on porosity testing, see ISO 10308, Metallic coatings — review of porosity tests); _ applicable where the failure mechanism is other than pollutant gas corrosion such as in tin-coated separable contacts.

This International Standard specifies equipment and a method for using nitric acid vapour to determine porosity in gold coatings, particularly electrodeposits and clad metals used on electrical contacts. This method is designed to show whether the porosity level is less than or greater than some value that, by experience, is considered by the user to be acceptable for the intended application. It is suitable for inlays or claddings containing 75 % or more of gold, for electrodeposits containing 95 % or more of gold or for substrates of copper, nickel and their alloys that are commonly used in electrical contacts. The nitric acid vapour test is too severe to be used for gold coatings less than 0,6 _m thick. It is also not suitable for coatings that are less noble than gold or platinum, such as palladium and its alloys, or gold-flashed palladium and its alloys. Several other porosity testing methods are described in ISO 10308 and in the literature (see e.g. Bibliography, [1] and [2]).

Specifies a method of revealing discontinuities and porosity in metallic coatings, where they penetrate the coating layer down to a substrate. Especially useful for coatings consisting of single or combined layers.

Lays down a method of revealing pores or other discontinuities, when testing metallic coatings, that are not visibly affected by ferricyanide and chloride ions during the test period and that are cathodic to iron and steel. This method is especially useful for thick, hard chromium coatings used for wear resistance.

Specifies the test solution, the apparatus and the procedure for a saline droplets corrosion test. Is suitable for detecting defests and discontinuities. It is also suitable for chemical or electrochemical conversion coatings. Is not suitable for testing coatings intended for the more severe types of service. The type and number of test specimens, the exposure periods to be used for a particular product and the interpretaiton of results are not specified.

Gives guidance on methods of corrosion testing of protective metallic, conversion and other non-organic coatings, with or without additive protection, in heated und unheated storage rooms in all microclimates with or without control of climatic parameters. Specimens and articles may be tested separately or in bilk, and with protective wrappings.

Specifies a rapid and accurate method for evaluating the corrosion resistance characteristics of electrodeposits on steel or zinc-base die casting designed for outdoor service. Does not describe exposure periods to be used for a specific product, nor the interpretaiton to be given to the results. Test conditions are provided to electrolytically dissolve the underlying coatings of nickel through discontinuities in the chromium overlay at such a rate that electrolysis for 2 min produces about the same extent of corrosion as does 1 year of service.

Specifies the reagent, the apparatus and the procedure for assessment of the quality of metallic and related coatings by the Corrodkode procedure. The method is primarily applicable to copper-nickel-chromium or nickel-chromium electroplated parts.

Reviews methods for revealing pores in a variety of metallic, inorganic and organic coatings. The tests summarized are designed to react with the substrat when exposed, by a discontinuity, in such a way as to form an observable reaction product.