Points to Consider for Laboratory Testing

Points to Consider for Laboratory Testing What are the main reasons for failures observed after laboratory tests on products coated with powder or liquid paint?   Many different paint-coated products are manufactured in our country for numerous sectors. In particular, the most significant tool that manufacturers currently use to enhance corrosion performance is paint. As is known, paints are applied to metal parts either as liquid or powder depending on factors such as the product's intended use, purpose, component dimensions, and so on. As an accredited test laboratory, based on test results, we can say that paint manufacturers have, through R&D efforts conducted over the past 10 years, successfully produced indoor or outdoor paints with desired properties (corrosion resistance, UV resistance, mechanical impact resistance, etc.) and are serving all related sectors successfully. When we begin discussing paint, it would be a significant oversight not to mention surface preparation processes—its counterpart, so to speak. The most important point to remember is that the better the surface treatment, the better the paint performance will be. Test result performance is directly related to whether these two companion applications are performed correctly. Surface preparation is, as is known, most commonly performed worldwide using two methods: mechanical surface preparation (abrasive blasting, sanding, etc.) or chemical surface preparation processes. Both companies producing and selling abrasive blasting materials and surface treatment chemicals have, through their work in parallel with developments in the paint industry, succeeded in producing surface preparation chemicals with significantly higher performance to obtain surfaces highly suitable for paint. With these new chemical products, time and economic savings are achieved, making it possible to obtain the paint-receptive surfaces required before painting. Reading the text up to this point, a manufacturer might think that since proven paints and similarly surface treatment chemicals exist, these products should always deliver successful results in laboratory environments conducting accelerated corrosion, mechanical, or environmental resistance tests that provide information about the process the product will undergo in natural conditions. Although theoretically this reasoning is sound, reality unfortunately is not always this way. What, then, are the fundamental causes of this situation? Certainly there can be many causes, but it is possible to say that a large portion of the problem lies in errors made during the surface preparation processes of metals before painting. It must be remembered that the greatest advantage of surface preparation is creating homogeneous areas where paint can adhere, thereby increasing metal-paint adhesion performance and consequently providing resistance to corrosive environments. On the other hand, the goal is to prevent corrosion progression from painted surfaces that open due to physical deformations (scratches, impacts, friction, etc.) occurring during the product's service life. In short, surface preparation processes directly affect corrosion performance. Based on observations from inspections I have conducted at manufacturers' facilities, I can summarize the basic errors made in the items below: a- Incorrect information that mechanical abrasive blasting removes rust, scale, and provides surface abrasion in addition to degreasing, b- Failure to select abrasive blasting materials appropriate for the metal surface, c- Foreign substances such as dust and dirt remaining on the surface after washing cleaning not performed following mechanical abrasive blasting, d- Unwanted contaminants such as oil and grease remaining on the surface due to failure to adhere to appropriate degreasing conditions in chemical processes, e- Failure to change rinsing water at the desired time intervals, f- Rust residue remaining on the surface due to ineffective cleaning in rust removal baths, g- Failure to provide surfaces of the desired quality in phosphate, chromate, nano-ceramic baths and absence of controls for this, h- Contamination caused by elements remaining on the surface due to poor quality of final rinsing water before painting (Ca, Mg, K, Cl, F, etc.), ı- Failure to perform passivation processes known to clearly enhance corrosion performance or performing them under inappropriate conditions, i- Failure to create neutral surfaces (pH: 5-8) required before painting, j- Incomplete drying before painting, k- Failure to perform routine controls mandatory in chemical processes generally, l- Failure to achieve required temperature in chemical processes, m- Reducing surface quality by extending the waiting period after surface preparation. As you will see in the items above, regardless of which path is followed, every step must be controlled effectively, required controls must be ensured, and records must be maintained. Here, the technical documentation provided by chemical manufacturers must be followed without fail, and care must be taken to strictly adhere to the desired concentration/time/temperature values. As can be seen, mechanical or chemical preparation processes are extremely demanding operations that, if not performed correctly, can result in numerous errors. Failure to carry out this process correctly will lead to numerous problems on the finished painted product that will shorten service life and reduce quality. Assuming surface preparation has been done correctly, the processes that must then be examined are the painting units. And we see that some basic errors are made in these processes as well. To list these: a- Failure to achieve the desired film thickness, excessive or insufficient film coating, b- Failure to homogeneously achieve the desired curing temperature or time in curing ovens, c- Buildup sticking to component surfaces resulting from lack of cleaning of dirt formed over time in curing ovens, d- Failure to achieve the desired static charge or malfunction of paint guns used in electrostatic systems due to remaining paint residue in suspension systems, e- Incorrect paint selection unsuitable for the purpose, f- Failure of paint to reach all surfaces on grooved or protruding components, incorrect paint process selection, g- Failure to perform required cleaning in paint shops at required intervals, impurities found on floors sticking to components through aeration before painting, h- Migration of lubricants such as oil and grease used in conveyor lines to components, i- Users transporting silicone and similar materials into the paint shop after working with them. As can be seen, paint units are also locations with many risks; these environments must be controlled strictly and all data must be recorded. There are many more problem sources than what I have written here. Therefore, obtaining quality products is only possible through approaching all processes with skepticism, controlling every operation, and maintaining records. The priority here is establishing an in-house quality control laboratory and conducting required initial tests at this laboratory with competent personnel, ensuring approval by manufacturers before products reach the market. In uncertain situations, coordination should be established with accredited laboratories to clarify results through comparative testing. The most important point to remember is that the quality you have achieved must be sustainable. As Metaltek Teknoloji Laboratuvarı, we continue to assist all our stakeholders through laboratory training we provide, on-site training conducted at companies' premises according to their requests, testing services, inspections, and recommendations we make for establishing an in-house quality control laboratory following these inspections. We are pleased to inform that we will continue to supply some testing equipment we have begun manufacturing and aim to increase production of in 2023 (Salt Spray Testing Equipment, Humidity Resistance Testing Equipment, Stone Throwing Testing Equipment, Water Jetting Testing Equipment, etc.) and other optional equipment at much more affordable prices to manufacturers in our country.     Tuncay Katırcı Chemical Engineer General Director Metaltek Teknoloji Laboratuvarı