![]() I just realized I didn't ask the follow up question that I referred to in my previous post. Molasses/water-no change in zinc 24 hours & counting Vinegar/water- zinc completely dissolved in 1 hourĬLR/water-zing dissolved completely in 15 minutes I placed a zinc plated fastener (all the same) in each container. Here are the acids I used: 1 pt white vinegar to 1 pt water, 1 part CLR to 1 pt water and 1 pt molasses to 10 pts water. I'm in the process of doing an experiment to see how quickly zinc plating will dissolve using three different diluted mild acids. Tom, thank you for responding to my question. One option is to have the part replated another is to strip the part of all coatings and apply zinc-rich paint, and a third option (often the most effective and least expensive) is to buy a replacement part. If you're seeing red rust it means most of the zinc is already gone, having performed its' purpose. And that's what happens when you put the article in any acid. The zinc was originally plated on the article to prevent it from rusting by sacrificial protection in other words, zinc, being more active, will dissolve preferentially to protect the steel. Further, full traceability to original manufacturing lot number is available.A. At Unbrako, we take a number of precautions to make sure over fasteners meet or exceed governing specifications. Unbrako is ISO 9001 & TS 16949 certified. Grade 8 or Class 10.9 fasteners are usually supplied with yellow chromate C3+ is hex avalent free. Clear, blue - bright, designation A or B trivalent chromates are normally used for Grade 5 or Class 8.8 fasteners. Chromate Conversion Coatingsįor use in moderate or severe environments, fasteners may be chromate-conversion coated for additional corrosion protection. Passivation is useful in strengthening and preserving the appear of metal. Passivation is the use of light coat of material such as metal oxide to create a shell against environmental factors such as air or water i.e. Thus no time is wasted in - between the processes, allowing for highest quality plating. High strength fasteners are particularly prone to hydrogen embrittlement because greater the strength (or hardness) of the alloy fasteners, the greater the susceptibility to hydrogen damage failure.Īt Unbrako the post-plating de-embrittlement baking is carried out on Fully Automatic Electroplating line with synchronized Auto loading system & hydrogen De-Embrittlement furnace & Passivation line. ![]() The electroplated coating traps the hydrogen inside the fasteners, which can migrate to areas of high stress and cause small microcracks & ultimately lead to brittle failure, unless they are baked soon after plating to drive the hydrogen out. Hydrogen Embrittlementĭuring acid cleaning and in the electroplating process, atomic hydrogen produced can diffuse into the steel and embrittle the structure of fastener. Because it's thin - It doesn't interfere with fastener threads. AdvantagesĮlectroplating results in smooth, shiny & drip-free surface - preferable for aesthetic reasons. The thickness of zinc plating depends on the time spent in the plating bath, the amount of electric current,and the chemical composition of bath. When direct current is applied, the zinc metal at the anode begins to dissolve, and the free metalions reach the cathode to form a thin layer of coating on the fastener. ![]() The fasteners are dipped in a chemical bath containing dissolved zinc. Thorough cleanliness is essential as the molecular layers of oil or rust can prevent adhension of the coating to the metal surface.Įlectroplating is done by the process of electro deposition. It is than treated with acid,in order to remove any rust or surface scales. Electroplating process starts with carefully cleaning the fastener surface in alkaline detergent type solutions.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |