More B The zinc coatings are classified according to thickness and identified into two types; as coated without supplementary treatments or with colored chromate conversion treatment. The thickest coating classes are usually referred to as "mechanically galvanized". All deposited coatings should have a bright uniform silvery appearance, and a matte to medium-bright luster. Samples should be tested for adhesion, salt-spray corrosion resistance, appearance, thickness, and absence of hydrogen embrittlement.
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Ii is the responsibility of the user of this standard to establish appr riaie safety and health practices und determine the applica: bility of regulatory limitations prior to use. Referenced Documents 2.
Pushed Mt che 6 Classification 3. Ordering Information 4. The coating shall be uniform in appearance and substan- tially free of pits, nodules, flaking, and other defects that can adversely alfect the function of the coating, The coating shall cover all surfaces as stated in 6. The coating shall not be stained or discolored throughout to an extent that would adversely affect appearance as a functional requirement, However, superficial staining, that results from to avoid the risk of producing hydrogen embrittlement from the cleaning procedure.
Useful guidelines are also given in Practice B 6. Preparation of the surface of the parts to be coated, by chemical generally acidie procedure to an extent that permits uniformly satisfactory results from subsequent steps.
There are no thickness require ments for this coating 6. Requirements 6. High-strength steels which become embrittled when charged with hydrogen and that have heavy oxide or scale shall be cleaned hefore application of the coating in accordance with Practice B , In general, nonelectrolytic alkaline, anodic-alkaline, and some inhibited acid cleaners are preferred 6. However, these are not normal in the leatmert eps preceding the application of the finish, When desired they mist be Specitied on the putehase onder Nom: Mechanical deposition is exchsively a barrel cess Is recounized that mechanieal epusition on parts my chetefore produce surfaces that ave dierent characteristic from those on pats that are Bnisbed exchisively by racking.
In such cases the purchaser shal indicace his regurements on the parchase order 4. For example, to reduce buildup in thread roots, holes, deep recesses, bases of angles, and similar areas, the deposit thickness on the more accessible surfaces will have to be reduced proportionately.
Such high-strength steel parts shall be free of hydrogen embrittlement. Properly per- formed, statistical process control will assure coated products of satisfactory quality and will reduce the amount of accep: tance inspection, The sampling plan used for the inspection of the quality coated article shall be agreed upon between the purchaser and producer.
The size of the sample and the criteria for compliance are determined by the application of statistics. Test Method B contains four sampling plans, three for use with tests that are nondestructive and one when they are destructive.
Test Method B provides a default plan if one is not specified. Guide B provides a default plan if one is not specified. Test Method B provides a default plan if one is not specitied. Therefore, before coated articles may be accepted.
Test Methods 8. The permission or the requirement to use test specimens, their number, the material from which they shall be made, and their shape and size shall be stated in the purchase order or other governing document 8. Removal shall be clone by using a very mild abrasive such as a paste of levigated alumina or magnesium oxide rubbed on gently with the finger. Nore 10—The process by which Type IL coatings are prodaced dissolves a small amount of the zine, For this reason the thickness reguiremen w be checked refers o the thickness ofthe deposi aller the pplication of the Type Tl coatings.
The ability 10 separate the coating from the substrate by peeling, as distinct from flaking caused by rupture of the deposit oF of the basis metal, shall be evidence of failure. One of the following methods for determining adhesion shall be used: Those given above are widely used: however, other tests may prove mote applicable in specie tases, Various qualitative methods are dfcussed in Test Method B STI. This is to permit uninterrupted exposure for the longer of the two test periods required without having to wash specimens for examination, in accordance with Prac- tice B 8.
R6 Absence of Hydmgen Embrittlement: 8. The description of the method shall include the means of applying a load to the part the stress oF load level to be applied, the duration of the test, the waiting time that must elapse between deposition of the zine and testing oF use of the part, and the eriterion of failure, 8.
Government reguite- ments shall be subjected to such loading conditions described above for ht minimum, Nore I2—It is recommended that fess for embritlement invelve subjecting pars tothe specified operating conditions for at least 10D h extepe ab noted in 8, High-carhon see!
Rejection shall be reported to the producer or supplier promptly and in writing, In case of dissatisfaction with the results of a test, the producer or supplicr may make a claim for rehearing. Certification The seven heaviest classes of eCitings offer suitable alternatives to hot-tip galva- nizing, The following data, based on widespread lesting, may hhe used to compare the behavior of zine in various atmo- spheres.
Mechanical Plating & Galvanizing
ASTM B695 Fasteners