Potassium Aluminum Fluoride (Flux) Residues and Interactions
Almost all the fluxes used show silicate reaction and sludge formation due to rapid onset of silicate reduction, which we could already see by the formation of jelly on the first and second sides. In addition, there is the permanently progressing surface corrosion of aluminum, as well as the formation of bulky corrosion products with embedded flux residues, which then leads to the already shown crumbs and blockages of the cooling channels. For the very interested I had a rough scheme of the respective influencing factors and their interactions.
Based on my first article, I would still like to show a concrete application scheme that also shows the percentages of the ingredients used in the coolant. Although to many the 40% glycol coolant (including corrosion inhibitors) may seem like a lot, the ratio used here shows the procedure for using aluminum radiators and the occurrence of higher temperatures. In a normal PC and with only copper in the circuit, the water content could of course be significantly higher. But glycol (along with inhibitors) doesn’t hurt either, and better safe than sorry.
Which brings us back to the cost of the coolant and, of course, what you get for your money and what is really resistant to flux influences. Unfortunately, quality has its price.
Summary and conclusion
What have we learned today? Potassium aluminum fluoride residues (fluxes) react with the corrosion protection additives (silicates) in the coolant. The silicate is consumed, the glycol forms aluminum hydroxide sludge, and the whole thing then clogs the ducts and pumps, which can lead to complete failure if the engine overheats. And what does that mean for the manufacturer? Even the smallest flux residues (potassium aluminum fluorides) in the radiator must be avoided! This in turn can be achieved with a suitable non-corrosive flux during brazing.
For a reliable cooling effect, subsequent internal surface rinsing and, ideally, passivation (e.g. coating) are also strongly recommended. When it comes to coolant, water-based coolant systems should be based on OAT glycol coolant, and if it can cost a little, you can even go for new coolants based on the “green chemistry” of organic fluoride liquids, which also promise highly efficient heat transfer from electronic components. The rest is done by the trusted paver.
Which then completes the cycle. If the company’s own manufacturer already buys in incorrectly in cost-down mode or has it manufactured by third parties, then even the best cardboard box won’t help. Corrosive fluxes in cheap aluminum radiators are not a solution but always the source of all evil. However, Apaltek is surely only the tip of the iceberg of those who, for cost reasons, pass on such products unseen, which actually have no place in a proper AiO. I had already written something about the victims on the provider side. It can affect anyone whose quality management is not equipped to deal with such products and the technical pitfalls that come with them.
My very special thanks go to the colleagues from the industry for their professional support and composure in the face of the damage that occurred, which normally should never have happened if good quality management were in place.
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