Index Membership Training WorkOpportunities Library Links About Us ContactUs Meetings Publications Buyer Guide Index Questions

If you have any inquiry related to metal finishing  feel free to post it here. Please click in the box to the right to open the form.  Answers will be published here.


Questions on Metal Finishing TechAsk

If you want to make contact with a responder, please use the form below:

Question #28

Click here to respond to this question         Submitted by: Olgierd      | Johannesburg RSA |  29/1/2016

I want to move away from heating elements to heat exchangers.

Is there a supplier out there?

Can anyone recommend a supplier?

Thanks in advance

Response #1 from the John Kleyn - Somerset West  Cape  February 2, 2016                Use form at top of page to contact this responder

Accurate Automation can assist with the design, supply, installation and commissioning of heatexchanger systems. We have many plants running on heatexchangers with Hot water boilers and heatpumps (Heating and cooling cycles). The energy source could be electric, LPGas, Natural Gas, Diesel or Electric heatpump. Our company does projects all over South AFrica. I refer you to the energy article in the SAMFA magazine. [Issue 24 - Page 40  from the Publications Tab above]

Response #2  from Struan Orlik- Johannesburg  February 2, 2016                                 Use form at top of page to contact this responder

After reading your question we can certainly be of assistance if required.

Before moving to heat exchangers have you considered the use of coils as they are low maintenance can be highly effective and would also not require maintenance.

Heat exchangers require a circulation pump from the solution through the exchanger , depending which one you use and then a hot water, oil or steam supply.

The other option is an in tank unit however they have certainly become quite expensive and are all typically imported.
Please advise which system you will look at implementing and we can assist where required.

Question #27

Click here to respond to this question         Submitted by: Viper  Q A Engineer     | Durban RSA |  4/6/2015

Good day, I require some help please. We are looking into connecting a steel tube to an aluminium tube. The aluminium tube is swaged so the steel tube would slide in by 20mm. Now I have researched and found no known welding method that would connect the steel to aluminium. My question is if we copper/zinc plate the steel would we be able to weld the 2 pipes to form a seal??

Response #1 from the J J - Gauteng   June 8, 2015                                           Use form at top of page to contact this responder

I believe the best option would be to apply a barrier between the steel and aluminium (zinc would seem most appropriate) to avoid galvanic corrosion, and to "weld" the joint by either friction stir welding (FSW) or direct heat (effectively soldering).

Friction stir welding was invented by The Welding Institute, Cambridge, UK, (tel: +44 (0)1223 899000); the local specialist (particularly aluminium) is Dr. Tony Patterson, contactable through the Aluminium Association.

At this point it is not possible to friction weld aluminium to steel directly due to considerable difference of their melting points (aluminium 660C/ steel 1370C; however advances have been made using galvanised steel and aluminium (zinc alloy melting point ~ 420C), where one would assume the zinc is fusing to the aluminium.

Question #26

Click here to respond to this question         Submitted by: Darrell Reeve Env Consultant to AISF   | Australia |  1/5/2015

I would like to invite SAMFA experts to solve a problem that many nickel electroplaters have in Australia.

The problem is that the nickel sulphate level increases with operation until the user has to dilute the bath to continue satisfactory operation.

There have been many suggestions made here and some proponents have been very definite but none seem to solve the problem properly:-

- pH – bright nickels used to run close to pH 4.5 but the newer processes run at 3.8 – 4.2 – more acidic and may cause the problem

- S nickel rounds cause the problem and pure, electrolytic, non S will stop the problem

- Increase the nickel chloride concentration above 60 g/l and the problem will stop

- Anode to cathode ratio is the solution to the problem – often anode surface area is too high

- Replace some of the nickel baskets with inert anodes

- Use eduction rather than air agitation

- Need to increase cathode efficiency to rectify the problem

- The problem does not appear with plating on plastics – only plating on steel, copper or ZBDC

I would welcome comments and reasons from any of your nickel plating or supplier members.

Response #2   from Trudy  | Chemical Supplier | Durban  Nov 6, 2015                              Use form at top of page to contact this responder

Dear Darrell, we do have the same problem. Nobody in RSA uses S-nickel. Newer technology nickels prefer the nickel chloride at 70g/ltr. This makes it worse. The chloride dissolves the anodes faster. They also prefer the pH to be lower (around 4), which also dissolves the anodes faster. Inert anodes might be a possibility, but at the cost of platinised titanium or similar, it is not really an option. Titanium creates an oxide layer and will not carry current. Carbon anodes react and drop the pH in the solution very quickly. After all this is said and done: not every plant has the problem and we do not know why. We have gone back to reducing the chloride to 60g/ltr and we run the pH in the upper 4 again, which seems to help. We start new nickel solutions with only 220g/ltr nickel sulphate. Unfortunately the "cleaner production and waste minimisation principal" of saving the drag-out and feeding it back into the plating tank makes it worse! Good luck and all the best Trudy

Response #1 from the SAMFA  advice desk   June 1, 2015                                         Use form at top of page to contact this responder

Hi Darrell, We have discussed this issue with several of our senior plating members. One of them is convinced that what works for him is to increase the anode to cathode area. The theory is that this lowers the current density across the anode resulting in slower corrosion. None of the other proposals appeared to be endorsed by any of them as a proven remedy.

Question #25

Click here to respond to this question                                              Submitted by: Savass   | Izmir Turkey |  7/4/2015

I’m looking for some tips on silver and cadmium plating. I’m trying to plate cadmium and silver on fasteners. The first problem is related to silver. We plate the silver on every surface of the screws except the top of the thread (major place). I haven’t any solution.

I’m using a barrel plating system. Its steps are: electrolytic, pre nickel, nickel, pre silver, silver. I used sand blasting to prepare my surface, then alkaline cleaning. Do you have any idea why there is not any silver on top of the thread?

Response #1 from Trudy - Plating Chemical Supplier - Durban RSA                             Use form at top of page to contact this responder

Dear Savass, silver in a cyanide solution normally throws very well. Is the article clean? Does the nickel plate in those areas? The lack of throwing power could be current related (i.e. is your rectifier suitable for barrel plating?) or your silver solution is out of balance.

All the best

Response #2 from Madhatter - Electroplater- Gauteng RSA                                         Use form at top of page to contact this responder

Have you tried to skip the sandblasting stage and just use soak..acid.. as a pre cleaner? It could be making your steel too porous and in a barrel the Nickel could be chipping off. At what stage is it noticeable that the items are not plating?

What is the question for Cadmium plating?

Question #24   Click here to respond to this question                                                           Submitted by: Kassie | KZN RSA |  4/10/2014

I got some equipment for electroplating. I want to start a small business. I need some assistance from anyone to help me to get going.

Response #1 from the SAMFA  advice desk                                                                      Use form at top of page to contact this responder

Your question is a bit vague. You haven’t mentioned what sort of equipment you have acquired, and what type of plating you intend taking on. But before you even start, there are some important considerations. The electroplating industry works with many different chemical solutions, many of which are aggressive, or toxic and a danger to the environment. Your plating plant has to be designed in such a way that you prevent any of these chemicals from harming the environment. If you are plating, then you will generate effluent. There are strict regulations governing what you may and may not discharge. Limits on metals dissolved in the waste water leaving your plant are measured in parts per million, and if you do not manage your waste water so that metals are below the discharge limits you open yourself to heavy fines and prosecution.

In addition, the premises where you intend to do this plating have to be approved by the Metro to enable you to get a license to discharge, without which you cannot operate legally, and you could be closed down before you start.

If the plant you have acquired does include an operational effluent treatment plant, and if you apply for a discharge permit from Metro and it is granted, then you will be able to get help from any one of the vendors operating in KZN. Please see the Buyers Guide on this site. Click here to be redirected to that page.

Question #23   Click here to respond to this question                                                   Submitted by: Nuova | Gauteng RSA |   19/05/2014

I need a supplier that can supply me the chemicals to alodine to RoHS MIL-C-5541 Type II spec. Gauteng or nationwide.

Question #22   Click here to respond to this question                                               Submitted by: Dylan Naaido | KZN RSA |   21/11/2013

I am looking for good quality G clamps that I can use in my anodising plant.

Please contact me if you can help or know of where I can source them.


Response #1 from Mark | Anodiser | JHB                                                                       Use form at top of page to contact this responder

Hi there, I have a supplier in Cape Town. Please contact me and I will send you the details.

Question #21   Click here to respond to this question                     Submitted by : J B Specmech | Pretoria RSA  | 13/11/2013

My company wants to audit our powder coating firms on their pre-cleaning and powder coating processes. I need to know according to what do we audit them? How many steps and processes they should have and follow. I am so out of my comfort zone on this one. Please Help!!!!!!!  

Response #1 from Greg | Chemical Supplier | Benoni - RSA                                        Use form at top of page to contact this responder

The basic guideline to auditing any powder-coater would be to see if they are conforming to the guidelines set out by manufacturers of the products that they use and apply in their processes. These parameters are made by manufacturers to ensure that their product works properly and the end user gets what they require. One example could be temperature specification (for chemicals and powders)

From a chemical perspective, they should have all their pre-treatment specifications, should regularly test them and record those results.

From a coating perspective they should conform to the recommended coating thickness and curing cycles recommended by the paint manufacturers.

An essential part of any operation has to be environmental consideration and one can also see how effluent is treated and handled.

Your question asked how many steps should be in place. That would depend on the kind of work their customers require them to do. There are so many types of systems – spray or dip, iron or zinc. The powder coater could have an entry level one shot spray pre-treatment or a complex multi stage and multi-metal tank or spray line. The important thing is: The customer knows what kind of system is in place and that the powder coater can consistently produce the best that they can with that system. Not everyone can afford a “Rolls Royce” system and sometimes it might not even be financial - the factory that they are in might not support the space or energy requirements of the more complex systems. The controls, however, go a long way to achieving results because a good, well maintained iron phosphate plant can achieve much better quality than a poorly maintained and neglected multi stage zinc phosphate plant.

Question #20   Click here to respond to this question                            Submitted by:  Team  Machine | Gauteng | 1/11/2013

Does anyone know of a company that does ‘parkerising”?

Response #1 from Shane W. | Powder Coater | Cape Province                                   Use form at top of page to contact this responder

My understanding of the word is that the process has largely been replaced by zinc or manganese phosphating. Zinc phosphating is practiced widely in the powder coating industry, and many operators in RSA offer the finish. The final finish would either be oiled or coated with another top coat like an epoxy or similar.

Question #19   Click here to respond to this question                             Submitted by:  Anton | Gauteng | Director  23/7/2013

I had an enquiry for de-greasing of metal parts consisting of welded 20mm square tubing prior to spray painting. Maximum overall size is 1600 x 1600 x 800. The customer is washing the parts manually and is looking for an automated process. I am in the ultrasonic cleaning and vapour de-greasing field, but these solutions are too expensive for the application. Does anyone have a more cost effective solution?

Response #1 from Trudy  | Chemical Supplier | Durban                                               Use form at top of page to contact this responder

Hi Anton, preparation for this process can be done in aqueous solutions with proprietary additives. The number of tanks required depends on the dirt/ oil/ rust on the articles.  Please feel free to contact me for further information.

Response #2 from Dean | Powder Coater | Gauteng                                                     Use form at top of page to contact this responder

All power coaters have a pre-treatment line that prepares the surface for painting. Usually it involves more than just de-greasing. It is common practice to apply a phosphate coating or equivalent to prevent under paint corrosion and to provide an excellent surface for the paint to key onto.

The number of steps in the system will depend on the nature of the oils, greases and oxides that are present on the surface.

The actual degreasing step is usually a basic alkaline hot soak formulation running at a temperature of anywhere up to 80oC  Any one of the vendors supplying proprietary chemicals into the metal finishing market will be able to give you advice on this.

Click here to view older questions