{"id":14705,"date":"2020-01-05T00:51:47","date_gmt":"2020-01-04T23:51:47","guid":{"rendered":"https:\/\/verzinkshop.nl\/chemical-blackening-problems-and-solutions-for-iron-and-steel\/"},"modified":"2025-12-08T01:55:44","modified_gmt":"2025-12-08T00:55:44","slug":"chemical-blackening-problems-and-solutions-for-iron-and-steel","status":"publish","type":"post","link":"https:\/\/verzinkshop.nl\/en\/chemical-blackening-problems-and-solutions-for-iron-and-steel\/","title":{"rendered":"Chemical blackening problems and solutions for iron and steel."},"content":{"rendered":"\t\t
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Chemical blackening of iron and steel troubleshooting<\/h2>\n

In general, most problems in the chemical blackening of iron and steel arise from<\/p>\n

    \n
  • Not rinsing properly and thoroughly, leaving acids behind. You can see this especially on the threads of bolts. <\/li>\n
  • Drying the object during the process. The object must remain wet from etching to sealing and must not be dried between steps. If this does happen, the black oxide coating or the metal will oxidize faster due to contact with oxygen. <\/li>\n
  • Sealer not applied sufficiently or rinse water not completely expelled.<\/li>\n<\/ul>

    <\/div>\n

    It is very important that acids from any etching bath, or from the black oxide agent itself, are properly rinsed away. If acids remain, the metal will react to this during sealing or later and brown rust will occur. <\/p>\n

    Baking soda can be added to the final rinsing water, after the black oxide process and before the sealer, to neutralize residual acids. Then rinse the object well. <\/p>\n

    It is also important to make sure that, during sealing, the chosen sealer expels all the water and no moisture remains on the black oxide coating. Immerse the object in the sealer several times to expel the water. <\/p>\n

    Problems with the chemical blackening of steel and iron<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
    Problem<\/td>\nCause<\/td>\nSolution<\/td>\n<\/tr>\n<\/thead>\n
    Irregular finish<\/td>\nInsufficient surface preparation<\/td>\nProvide thorough cleaning and degreasing. Mechanical preparation such as sanding may be required. With etching, you get a uniformly clean finish.<\/td>\n<\/tr>\n
    Black oxide finish too light<\/td>\n\n
      \n
    • Low solution concentration<\/li>\n
    • Black oxide liquid depleted<\/li>\n
    • Extra hardened steel<\/li>\n<\/ul>\n<\/td>\n
    		\n
      \n
    • Adjust the concentration of the black oxide solution.<\/li>\n
    • Replace or refill the solution.<\/li>\n
    • Etch the object longer and better.<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n
    Coating rubs off<\/td>\nToo thick black oxide coating<\/td>\nShorten the process or dilute the liquid.<\/td>\n<\/tr>\n
    Spotty and non-uniform finish<\/td>\n\n
      \n
    • Contaminated solution<\/li>\n
    • Various metals fused together<\/li>\n
    • Hydrochloric acid used for etching<\/li>\n<\/ul>\n<\/td>\n
    		\n
      \n
    • Filter the black oxide solution or replace it.<\/li>\n
    • Unsolvable.<\/li>\n
    • Do not use hydrochloric acid at Verzinkshop Zwart Oxide. (can be done with Black Oxide Ultra) <\/li>\n<\/ul>\n<\/td>\n<\/tr>\n
    Bluish or grayish finish<\/td>\nInsufficient activation<\/td>\nPre-treat the metal with an etching liquid such as Verzinkshop Metal Activator or another acid.<\/td>\n<\/tr>\n
    Parts rust after treatment<\/td>\n\n
      \n
    • Acid from the etching or black oxide bath left behind<\/li>\n
    • Moisture in the sealer<\/li>\n<\/ul>\n<\/td>\n
    		\n
      \n
    • After each step, rinse the object very well. Add baking soda to the final rinse bath to neutralize any remaining acids, then rinse well again. <\/li>\n
    • Submerge the object several times during sealing to expel all water from the object.<\/li>\n
    • Drain water that collects at the bottom of the sealer tank.<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n
    Poor adhesion<\/td>\n\n
      \n
    • Surface not activated properly<\/li>\n
    • Too thick layer<\/li>\n<\/ul>\n<\/td>\n
    		\n
      \n
    • Activate the object longer or use a stronger etching agent.<\/li>\n
    • Shorten the process.<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n
    Thick Releasing Layer<\/td>\nToo long treatment<\/td>\nShorten the immersion time in the black oxide solution or dilute the liquid.<\/td>\n<\/tr>\n
    Dark streaks<\/td>\n or markingsIrregular application<\/td>\nMake sure the parts are completely submerged and agitated.<\/td>\n<\/tr>\n
    Rapid discoloration<\/td>\nInsufficient rinsing<\/td>\nRinse the object very well and do not let it dry between steps.<\/td>\n<\/tr>\n
    Residual oil after sealing<\/td>\nExcessive application of the sealer<\/td>\nApply less sealer, shake the object well after sealing to remove excessive sealer.<\/td>\n<\/tr>\n
    White spots<\/td>\nHard water or mineral deposits<\/td>\n\n
      \n
    • Rinse with demineralized or distilled water.<\/li>\n
    • Make sure that all water has been expelled when the sealer is applied.<\/li>\n
    • It is better to shake the object before applying the sealer.<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n
    Corrosion stains during the process<\/td>\nDrying black oxide coating without sealer<\/td>\nMake sure that the object between the acid bath and the sealer is not dry; the object must remain wet from the acid bath onwards, otherwise it will oxidize due to oxygen.<\/td>\n<\/tr>\n
    Reaction stops prematurely<\/td>\nSolution Exhausted or Contaminated<\/td>\nChange the black oxide solution.<\/td>\n<\/tr>\n
    Spotty and not uniform black<\/td>\n\n
      \n
    • Insufficient cleaning<\/li>\n
    • Insufficient rinsing<\/li>\n<\/ul>\n<\/td>\n
    		\n
      \n
    • Remove the black oxide layer. Clean and rinse the part well. Remaining fats, acids, fingerprints or cleaning agents cause problems. <\/li>\n
    • Be sure to clean the parts thoroughly.<\/li>\n
    • Check for water breaks on parts during rinsing.<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n
    Bluish glow on parts or gray finish<\/td>\nInsufficient activation<\/td>\nCarbon steel, 4130 and parts that result in a grey finish may require more time in Galvanising Shop Metal Activator or the chosen acid bath. A longer time in the black oxide can also help.<\/td>\n<\/tr>\n
    Excessive abrasion<\/td>\nImproper blackening<\/td>\nCheck the strength and duration of the blackening solution; adjust if too strong or too long. Make sure parts are clean before blackening.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Tips for cold chemical blackening of metal<\/h2>\n

    Checking the metal: Inspect the metal surface under adequate lighting to identify rust, shell, and contaminants that may interfere with the processes.<\/p>\n

    Degreasing the metal: use a solvent or alkaline detergent to remove grease and oil. Ultrasonic cleaning can be beneficial for complicated parts. Do not use an oil-based cleaner. <\/p>\n

    Remove rust: Apply rust removers or use mechanical methods such as sandblasting, wire brushing, or manual sanding for heavy rust.<\/p>\n

    Chemical activation and etching: treat the metal with an acid pickling solution to lightly etch the surface and improve adhesion. Pay attention to the concentration and time to avoid over-etching that can damage the metal. You can use Verzinkshop Metal Activator for this. <\/p>\n

    Solution preparation: ensure that the black oxide solution is mixed with distilled or demi water according to the specifications in the manual. Store it in a sealed container so you can use the liquid again later. <\/p>\n

    Chemical blackening applications<\/h2>\n

    Immersion: For even coverage, fully immerse the component in the solution. Agitation can help to achieve an even layer. <\/p>\n

    Brush, sponge or cloth: for large parts or repairs, apply the solution with a brush for example, ensuring even coverage and minimal dripping.<\/p>\n

    Observe the color change and reaction progression. Adjust the immersion time and liquid strength based on the desired color depth. <\/p>\n

    Rinsing and neutralizing the parts<\/h2>\n

    After an acid or black oxide treatment, acid can still remain in threads, holes and cracks. If you seal afterwards, it can cause brown corrosion later. Prevent this with a short neutralizing rinse. <\/p>\n

    Procedure<\/h3>\n
      \n
    1. Rinse thoroughly to remove residue.<\/li>\n
    2. Neutralize:\n
        \n
      • Preferred: 1 to 2 percent sodium bicarbonate (baking soda), 10 to 20 g per liter, 30 to 60 seconds dipping.<\/li>\n
      • Alternative: 0.5 to 1 percent sodium carbonate (crystal soda), 5 to 10 g per liter, dip for 15 to 30 seconds.<\/li>\n<\/ul>\n<\/li>\n
      • Rinse well again immediately, preferably with demi water.<\/li>\n
      • Do not allow to dry between acid or black oxide bath and sealer; Seal immediately.<\/li>\n<\/ol>\n

        Do not rinse under the tap; Use a flow-through or overflow sink.<\/p>\n

        Sealing and finishing the conversion coating and metal<\/h2>\n

        Oil finish: apply an oil for parts that require lubrication or rust protection. Provide full coverage. For example, use Verzinkshop DeepSeal Oil Metal Sealer, which dries dust-dry. <\/p>\n

        Wax finish: for decorative items, you can also use a clear wax to apply a protective layer.<\/p>\n

        Acrylic paint finish: Electrolyte shop Acrylic Sealer is a very thin satin to glossy acrylic paint that dries without structure and is almost invisible. Ideal for indoor applications. <\/p>\n

        2K paint finish: for items that are exposed to harsh conditions, a high-quality 2K paint offers durable protection.<\/p>\n

        Curing: Allow the seal to cure according to the product’s instructions. This step is crucial for durability and wear resistance. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"

        Chemical blackening of iron and steel troubleshooting In general, most problems in the chemical blackening of iron and steel arise from Not rinsing properly and thoroughly, leaving acids behind. You can see this especially on the threads of bolts. Drying the object during the process. The object must remain wet from etching to sealing and […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[950],"tags":[942,952,951],"class_list":["post-14705","post","type-post","status-publish","format-standard","hentry","category-steel-and-iron-chemical-blackening","tag-chemical-blackening","tag-chemical-blackening-problems","tag-problems"],"acf":[],"_links":{"self":[{"href":"https:\/\/verzinkshop.nl\/en\/wp-json\/wp\/v2\/posts\/14705","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/verzinkshop.nl\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/verzinkshop.nl\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/verzinkshop.nl\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/verzinkshop.nl\/en\/wp-json\/wp\/v2\/comments?post=14705"}],"version-history":[{"count":0,"href":"https:\/\/verzinkshop.nl\/en\/wp-json\/wp\/v2\/posts\/14705\/revisions"}],"wp:attachment":[{"href":"https:\/\/verzinkshop.nl\/en\/wp-json\/wp\/v2\/media?parent=14705"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/verzinkshop.nl\/en\/wp-json\/wp\/v2\/categories?post=14705"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/verzinkshop.nl\/en\/wp-json\/wp\/v2\/tags?post=14705"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}