Metal Surface Pretreatment-101
The Cleaning Processes
The metal surface pretreatment process plays an important role before painting. In that process, there are several steps. To ensure excellent metal-painted surface quality. The metal cleaning is the first step before any further surface treatment activities. This step will help reduce residue (metal or dust, oil, grease, and various rust prevention substances) and increase the wettability of the metal surface; this feature meets the requirements of the following process steps.
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| Steel Plate Cold Rolled Commercial (SPCC) are soaked in an acid cleaning solution for degrease. (Cleaning Products of Tema Coating and System Company Limited, Manufacturer and Distributor in Thailand) |
There are many types of products for cleaning metal surfaces such as:
Acid cleaners’ type:
To removes oils and light metal oxides from metal surfaces by using acidic solution which has a pH < 7.0 in clean water: Tap water/ Reverse Osmosis water/ Distilled water / Deionized water combined with solvents, cleaner, wetting and emulsifying agents. For remove thicker oxides, rusts, and scales may be using strong acid for acid etching of thicker oxides, rusts, and scales on metal surfaces
Alkaline cleaners’ type:
To remove oils and various stains from metal surfaces by using an alkaline or base solution, which of course will have a pH >7.0 in clean water, Tap water, reverse osmosis water, distillated water, and deionized water are combined with solvents, cleaners, wetting agents, and emulsifying agents. If alkaline cleaner consists of sodium hydroxide (NaOH) or potassium hydroxide (KOH), it’s more likely to cause a saponification reaction occurs when it reacts with oils or fats. Saponification [1] can be defined as a “hydration reaction where free hydroxide breaks the ester bonds between the fatty acids and glycerol of a triglyceride, resulting in free fatty acids and glycerol,” which are each soluble in aqueous solutions. This process specifically involves the chemical degradation of lipids, which are not freely soluble in aqueous solutions.
Solvent cleaners’ type:
Many solvents offer the advantage of quick cleaning, so the oils and various stains dissolve and flow off of the metal surface without needing extended prep time, processing time, or drying time. Solvent-based cleaners remain widespread in industrial applications due to their cleaning power. Some examples of strong cleaning solvents are acetone, toluene and trichloroethylene (TCE). Some examples of mild solvents include isopropyl alcohol, glycerin, and propylene glycol.
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| Steel Plate Cold Rolled Commercial (SPCC) after soaking in an acid cleaning solution for degrease (Cleaning of surface) (Cleaning Products of Tema Coating and System Company Limited, Manufacturer and Distributor in Thailand) |
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| Steel Plate Cold Rolled Commercial (SPCC) after soaking in an acid cleaning solution has Surface tension test by using DYNE TEST PENS, DYNE TEST INKS: FOR TESTING SURFACES TENSION (According to DIN 53364, ASTM D2578 [2]) |
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