About
29
Sep 2016

What’s on the Plate?

The Lowdown on Zinc Plating

This past week, I caught up with Mr Zakir Hossain (ZH), our Sales & Technical Manager, to talk about one of the most common and low cost electroplated coating processes. Zakir has more than a decade of experience in the electroplating industry, and is often known for his knowledgeable insights in the field.

Zakir Hossain, Sales & Technical Manager
Zakir Hossain,
Sales & Technical Manager

KWY: So my first question is, how do I achieve a better quality finish on my parts?

ZH: What I learnt since my days as a process engineer, is that the pre-treatment process is very important. The right degreasing chemical will help to remove surface oils thoroughly. It can save a lot of time and cost with the cut down of reworked or rejected parts per batch. This, to me, is the best and easiest way is to guarantee a great finish on the plated parts.

KWY: What is the consequence of not removing grease/machining oil properly?

ZH: Well, the parts will definitely still be plated! However, after a few days, blistering will occur as the plated layer faces adhesion problems. This is a common problem faced by many of our customers.

KWY: So does the quality of the degreaser chemical affect the parts in a big way?

ZH: Definitely a shorter dipping time – assuming the parts are the same. The degreaser’s lifespan still depends on how oily the surface of the material is so that’s a bit harder to determine. But using a more effective degreaser means higher parts per hour output on the production so surely you can get significant cost savings.

KWY: How do I know if my parts is thoroughly cleaned?

ZH: In general, you can visually inspect for any residual oil stains after the degreasing stage. But for better measure, I like to use something called the “Water Break Test”. Dip the part into a water rinse tank, if the water droplets seem to fall off the surface quickly and there are little or no droplets left on the surface, then there is still some residual grease, simple and effective!

KWY: What is the minimum plating thickness of Zinc Plating?

ZH: Based on general zinc plating specifications, the plating thickness required by clients usually falls between 8-10 Microns.

KWY: What are some of the best practices or things to take note of to achieve an even zinc plated surface on my base materials?

ZH: Generally, the quality of the plating bath and also good control of the plating parameters are some things to take note of. However, there are also  other factors such as:

  • The right concentration of the bath chemicals depending on the acid type (i.e. Ammonium Chloride) or the Alkaline type (i.e. Caustic Soda). Usually the range falls between 80-120 grams/litre.
  • Maintaining a high quality chiller. I cannot stress enough how important good temperature control practices are. When the temperature control is not done properly, a bath that is too hot can cause burn marks which are visible on the surface of the plated material. Conversely, when it is too cold, the plating time will be longer and thus affect the efficiency of the bath. Things like higher energy and material cost would be incurred in the process.
  • Using of good quality chemical additives. Here at C&M, we always emphasize how good chemical additives help improve the throwing power in the bath which would improve the rate and quality of deposition on the surface.
  • Auxiliary Equipment such as having a good rectifier can help maintain an accurate and constant current in the bath. I’ve had experiences whereby the meter reading of 12 volts turns out to be significantly less at the end of the wires where I used a tong meter to measure! In addition, by having a chemical filtration system in the bath, it really helps to remove any impurities that may arise during production and help to counter against any contamination issues. A proper jig designed with good contact points will also avoid problems such as sparking and slow plating speed due to bad current flow.

KWY: At the passivation step, why do I get differing results on the color and quality of my parts?

ZH: There are 2 possible reasons that come to mind. First, the pH level of the passivate chemical. Usually, at high pH levels, we are unable to get the desired color tone as the solution becomes too alkali and its effectiveness is significantly reduced. Conversely, when the pH level is too low, the right color tone is difficult to obtain due to the instability of the bath as a constant dipping time yields a different shade.

Second, the quality of the passivation chemical. Of course, with more stringent specifications and higher quality zinc plating requirements, only a couple of products on the market can truly deliver results which meet and surpass various anti-corrosion tests. C&M happens to carry a few of these products too.

KWY: Zinc Plating has such a wide rage of applications, so how do you advise your customers on which products to use?

ZH: My team and I will analyse the specifications that they require such as the colors (Black, Yellow, or Blue), or the type (Hexavalent, or Trivalent). As with all processes, we will recommend a suitable list of process chemicals and materials which we feel are the right fit in terms of its quality and price. But most importantly, we will be there personally at every step of the way to ensure that their production will run smoothly and see a marked improvement after using our recommendations. That is what makes our work challenging every single day!

KWY: Thanks for taking the time off to have a chat with us!

ZH: You are welcome.


Kwan Wai Yew (KWY) is the Sales Director of Chemicals & Machinery. Despite having recently graduated with a BA (Hons) in Business Economics (UK), Wai Yew is no new comer to the Surface Finishing industry. Besides having a knack for sales, he is also passionate about sneakers and a bona fide petrolhead.