From prep to final coat. Discuss it here

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Painters Institute
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Joined: Fri Apr 20, 2012 2:21 am


Post by Painters Institute » Tue Jun 25, 2013 2:27 am

Corrosion as a natural process commonly known as 'rust' or 'rusting' on metal surfaces such as Iron or Steel is often a problem for the Painter. It is a major problem for the Protective Coatings Industry in terms of its financial cost and its removal by means of suitable Protective Coatings. The Domestic Painter will often encounter corrosion in preparing and repainting of such metallic surfaces such as galvanized iron and various ferrous metals such as iron and steel. These are all used in guttering, downpipes, fencing, balustrades and of course roofing. But what is Corrosion you may well ask?
Corrosion is defined as" the destruction or deterioration of a material because of its reaction with the environment". Hence, corrosion is usually chemical in nature and demonstrates the tendency of steel which is made from iron ore found in the natural world to revert back to its original state as iron ore. Such a natural process is visually observed by the presence of rust or rusting which is a term reserved for corrosion of iron and steel and may be known chemically as ferric hydroxide (Fe(OH)3).

From the foregoing we see that corrosion is a chemical process because of the reaction of a metal with its environment which forms other compounds, such a reaction is electrochemical or more commonly known as electrolytic. This reminds us of the simple function of a battery which by means of a chemical reactions causes an electric current to flow which is utilized for some work. This simple example illustrates the benefits of the corrosion process.

The corrosion process consists of four major components well illustrated by means of a simple dry cell or wet cell battery. These are the anode, the cathode, conductor which connects the anode and cathode and the electrolyte which is the chemical or solution in which the anode and cathode are immersed. Further explanation of these will be in a future article.

Neil Mc Fadzen
National Institute of Painting and Decorating
Cert 3 in Surface Preparation and Coating Application TAFE
NACE Coating Inspector Level 2-Certified

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Re: Corrosion

Post by daniel.wurm » Thu Apr 21, 2016 1:12 am

Rust Converters

Many painters think that rust should be treated by using a rust converter.

However, the standard AS/NZ2312:2002,'Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings', says “There is a considerable amount of published literature which refutes such claims, stating that where any conversion may occur, complete penetration of rust and reaction with it is unlikely.”

The Standard states that the use of a ‘rust converter’ with any coating systems quoted in AS2312 Table 6.3 (coating systems for direct application to hand-cleaned and power-tool cleaned rusty steel) is NOT recommended, and will detract from their subsequent performance.

If you are using rust converter you are wasting your time and money! The only way to treat rust properly is to remove it and to use rust inhibiting primers. ... erters.pdf

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