Issues to Consider for Laboratory Tests
In our country, Turkey, many different paint-coated products are produced for many different industries. In particular, the biggest instrument that manufacturers currently
use to increase corrosion performance is, paints.
As it is known, paints are applied on metal parts either as wet or powder, as a result of factors such as the place of use of the product, its purpose, the size of the parts, etc.
Depending on the test results, as an accredited test laboratory owner, I can definitely say that paint manufacturers can produce and successfully serve great indoor or outdoor paints with the desired properties (corrosion, UV resistance, resistance to mechanical effects, etc.) to all related industries.
When we start talking about paint, it would be a big mistake if we don’t talk about surface preparation, which is what I call its “sister.” The most important point to remember is that the more successful the surface treatment is, the more successful the paint performance will be.
Test result performances are directly related to whether these two sister applications are done correctly. As it is known, all over the world, surface treatment preparation is made by using two methods, namely mechanical surface preparation (sandblasting, sanding, etc.) or chemical surface preparation processes.
In parallel with the developments in the paint industry, companies that produce and sell both sandblasting products and surface treatment chemicals have succeeded in producing surface preparation chemicals with much higher performance to obtain surfaces that are very suitable for paint. With these new chemical products, while obtaining time and economic savings, it is possible to achieve paint-holding surfaces required before painting.
When we read this article from the beginning to this point, the manufacturer may think that since there are paints and similar surface treatment chemicals that have already proven themselves, these products are always should be expected to yield good results.
Although this idea is theoretically correct, the reality is unfortunately not always this way. So, what are the main reasons for this situation?
Of course, there may be many reasons for this, but it is possible to say that the problem is mostly the mistakes made in the surface preparation processes of the metals before
painting.
It should be noted that, the biggest advantage of surface preparation is to increase the metal-paint adhesion performance by creating homogeneous areas where the paint can be adhered, thus providing resistance against corrosion environments.
On the other hand, it is desirable to prevent the progression of corrosion from the
paint surface opened by physical deformations (scratches, impacts, abrasions, etc.) occurring during the life of the product. In short, surface preparation processes directly affect corrosion performance.
Through my observations while I inspect the manufacturers’ facilities, I can summarize the main mistakes made, as follows:
a- Incorrect information believing that the mechanical sandblasting also causes degreasing in addition to rust, oxide removal, pickling,
b- Not choosing suitable sandblasting materials for the metal surface,
c- Off substances such as dust, dirt, etc. remaining on the surface after washing cleaning not done after mechanical sandblasting,
d- Unwanted impurities such as oil, grease, etc. remaining on the surface due to failure to comply with the appropriate degreasing conditions in chemical processes,
e- Not changing the rinsing waters in the desired time period,
f- Rust residues remaining on the surface as a result of ineffective cleaning in the rust removal baths,
g- Not providing the desired quality surfaces in phosphate, chromate, nano ceramic baths and lack of controls,
h- Pollutions formed by the elements remaining on the surface due to the low quality of the final rinsing water before painting (Ca, Mg, K, Cl, Fl etc.)
I-Passivation processes, which are clearly known to increase corrosion performance, are not carried out or not carried out under appropriate conditions,
i- Not creating the neutral surfaces (pH: 5-8) required before painting, j- Incomplete drying before painting,
k- In general, the obligatory routine controls in chemical processes are not carried out,
l- Failure to provide the required temperature in chemical processes,
m- Reducing the surface quality by keeping the waiting time long after surface preparation.
As you will see in the above articles, whatever path is followed, every step must be effectively controlled, necessary controls must be provided and recorded. Here, the technical documents provided by the chemical manufacturers must be followed, and attention must be paid to fully complying with the desired concentration / time / temperature values.
As it can be seen, mechanical or chemical preparation is a process that requires extreme attention and can cause many errors to arise in the opposite case. Failure to perform this process correctly will lead to many problems that shorten the life of the finished product and reduce the quality.
Assuming that the surface preparation is done correctly, of course, there are processes and paint units that need to be examined from now on. And we see that some fundamental mistakes are made in these processes.
To list them;
a- Not providing the desired film thickness, high or low film coating,
b- The desired curing temperature or time is not provided homogeneously in the curing ovens,
c- As a result of not cleaning the impurities formed over time in the curing ovens, sticking to the surfaces of the parts,
d- Failure to obtain the desired staticity due to paint residues remaining in the hanger systems used in electrostatic systems or malfunctions of the paint gun used,
e- Wrong paint selection that is not suitable for the purpose,
f- Paint does not reach every surface on recessed and protruding parts, wrong paint process selection,
g- Necessary cleaning in the paint shops is not carried out in the required time, the impurities on the floor become airborne before the paint and stick on the part,
h- Spread of lubricating elements such as oil-grease used in conveyor lines to parts,
i- After dealing with silicone and similar structures, carrying these into the paint shop.
As it can be seen, paint units are places with many risks, thus, these environments must be strictly controlled and all data must be recorded. Actually, there are many more sources of problems exist which we have not discussed in this paper.
Therefore, obtaining quality products can only be achieved by approaching all processes with suspicion and by controlling and recording every process. The priority here is the establishment of a preliminary quality control laboratory in the facility and the first tests required in the presence of competent personnel are carried out in this control laboratory
and the products should be approved by the manufacturers before releasing to the market.
In doubtful cases, the results should be clarified with the compare tests to be carried out in
coordination with the accredited laboratories. The most important issue to remember is that the quality you provide must be sustainable.
We, as Metaltek Technology Laboratory, continue to help all our stakeholders with the in-laboratory trainings or according to the requests of the companies the trainings, the test services, the audits we provide in their institutions.
And the suggestions we make for the establishment of a pre-quality control laboratory after
these inspections. We would like to inform you that we will continue to supply the test devices (Salt Fog Tester, Humidity Resistance Tester, Stone Chip Tester, Water Jetting Tester, etc.) and other optional devices to our manufacturers in our country Turkey at much more affordable prices, which we started to produce and aim to increase our production in 2023.
Tuncay Katırcı
Chemical Engineer
General Manager
Metaltek Teknoloji Laboratuvarı
