{"id":85,"date":"2013-10-15T05:12:27","date_gmt":"2013-10-15T05:12:27","guid":{"rendered":"https:\/\/advancedplatingtech.com\/?page_id=85"},"modified":"2022-02-24T00:20:40","modified_gmt":"2022-02-24T06:20:40","slug":"aluminum-chromate-conversion-services","status":"publish","type":"page","link":"https:\/\/advancedplatingtech.com\/electrolytic-plating\/aluminum-chromate-conversion-services\/","title":{"rendered":"Aluminum Chromate Conversion Coatings"},"content":{"rendered":"

Aluminum Chromate Conversion Coatings per MIL-C-5541 (MIL-DTL-5541) and ASTM B449-93<\/h2>\n

** Advanced Plating Technologies no longer offers chromate services as a final finish. Please use the below content for reference only **<\/strong><\/em><\/span><\/h2>\n

\"Aluminum<\/a><\/p>\n

The chromate process provides a clear iridescent to slightly golden iridescent film of low contact resistance.\u00a0 The corrosion performance of our aluminum chromate conversion coating is consistent with that of traditional hexavalent processes and is largely a function of the specific alloy that the aluminum chromate conversion coating is applied to.<\/p>\n

Aluminum chromate conversion coatings improve the corrosion resistance of wrought, heat treatable and cast aluminum alloys while providing an excellent base for subsequent painting or powder coating services<\/a><\/span>.<\/p>\n

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Aluminum Chromate Conversion Coatings –\u00a0Aluminum Chromate Conversion Coatings Properties<\/h2>\n

** Advanced Plating Technologies no longer offers chromate services as a final finish. Please use the below content for reference only **<\/strong><\/em><\/span><\/h2>\n

Aluminum chromate conversion coatings, often referred to as chemical film<\/b> or under the trade names Alodine<\/b> or Irridite, <\/b>produce a thin coating in the range of 0.00001-0.00004 inches in thickness.\u00a0 Aluminum chromate conversion coatings are amorphous in structure with a gel-like composition hydrated with water.\u00a0 This characteristic provides aluminum chromate conversion coatings with a unique self-healing characteristic if scratched or abraded.\u00a0 Metal exposed from a scratch slowly becomes covered by soluble chromate from areas adjacent to the scratch.<\/p>\n

\"Aluminum<\/a>Due to the extremely thin nature of aluminum chromate conversion coatings there is no practical way to measure the coating thickness or adhesion.\u00a0 Generally the adhesion of the aluminum chromate conversion coating can be determined by evaluation of secondary paint applied to the chromated aluminum.\u00a0 Standardized tests of this nature are addressed in ASTM test methods D3359 or ISO 2409.<\/p>\n

The electrical contact resistance of aluminum chromate conversion coatings is low, with Class 3 coatings per MIL-C-5541 being the lowest.\u00a0 Typical contact resistance of Class 3 aluminum chromate conversion coatings is less than 5,000 microhms per square inch as applied.\u00a0 The surface roughness and flatness of the test pieces can have a significant impact on this value.<\/p>\n

Corrosion resistance of aluminum chromate conversion coatings is highly dependent on the specific alloy employed.\u00a0 As a rule, the more pure the aluminum alloy is, the better the chromated product will perform in corrosion tests.\u00a0 For example, the same aluminum chromate conversion coating applied to a wrought aluminum alloy (such as 1100 series) can exceed 200-hrs in neutral salt testing per ASTM B117 as compared to less than 24-hrs for a cast aluminum alloy with silicon content exceeding 1%.<\/p>\n

The appearance of aluminum chromate conversion coatings is also largely dependent on the specific alloy chromated.\u00a0 In fact, five unique alloys processed with a consistent pretreatment and application of chromate can produce five distinct hues of chemical film. \u00a0Cast aluminum alloys typically have the widest variation and inconsistencies in appearance due to the high percentage of alloying constituents within cast aluminum grades. \u00a0ASTM B449-93 makes special note of this point in section 4.2 stating, \u201cIt should be noted that color and color uniformity will vary somewhat between one alloy and another and from a polished surface to an etched surface.\u201d<\/p>\n

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Aluminum Chromate Conversion Coatings – Specifications<\/h2>\n

\"Aluminum<\/a>The two most common aluminum chromate conversion coatings certified are MIL-C-5541 and ASTM B449.\u00a0 A summary of chromating services per the ASTM and MIL specs is as follows:<\/p>\n

Aluminum Chromate Conversion Coatings to MIL-C-5541 (MIL-DTL-5541)<\/strong><\/h3>\n

Type I \u2013 Compositions containing hexavalent chromium
\nType II \u2013 Compositions containing no hexavalent chromium<\/p>\n

Class 1A \u2013 For maximum protection against corrosion, painted or unpainted
\nClass 3 \u2013 For protection against corrosion where low electrical resistance is required<\/p>\n

Aluminum Chromate Conversion Coatings to ASTM B449-93<\/strong><\/h3>\n

Class\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Appearance \u00a0 \u00a0Coating Mass (g\/m2) \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Corrosion Protection
\n<\/span><\/b>1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Yellow to Brown \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 0.4 to 2 g\/m2\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Maximum as Final Finish
\n2\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Colorless to Yellow \u00a0 \u00a0 \u00a0 0.1 to 0.4g\/m2\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Moderate as Paint Base
\n3\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Colorless \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0< 0.1\u00a0\u00a0g\/m2\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Decorative, Slight
\n4\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Light Green to Green \u00a0 \u00a00.2 to 5 \u00a0g\/m2\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Moderate as Paint Base<\/p>\n","protected":false},"excerpt":{"rendered":"

Aluminum Chromate Conversion Coatings per MIL-C-5541 (MIL-DTL-5541) and ASTM B449-93 ** Advanced Plating Technologies no longer offers chromate services as…<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":360,"menu_order":0,"comment_status":"open","ping_status":"open","template":"","meta":{"_acf_changed":false,"jetpack_post_was_ever_published":false,"footnotes":""},"class_list":["post-85","page","type-page","status-publish","hentry"],"acf":[],"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/P7G6ce-1n","_links":{"self":[{"href":"https:\/\/advancedplatingtech.com\/wp-json\/wp\/v2\/pages\/85","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/advancedplatingtech.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/advancedplatingtech.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/advancedplatingtech.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/advancedplatingtech.com\/wp-json\/wp\/v2\/comments?post=85"}],"version-history":[{"count":0,"href":"https:\/\/advancedplatingtech.com\/wp-json\/wp\/v2\/pages\/85\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/advancedplatingtech.com\/wp-json\/wp\/v2\/pages\/360"}],"wp:attachment":[{"href":"https:\/\/advancedplatingtech.com\/wp-json\/wp\/v2\/media?parent=85"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}