The various grades are defined by written descriptions together with photographs that are representative examples within the tolerances for each grade as described in words. In addition, this part of ISO specifies both initial surface conditions and after-cleaning flash rust grades, also defined by written descriptions together with representative photographic examples. NOTE 1 Examples of foreign matter are salt, grime, dirt, mill scale, oil, grease and marine growth, e. This part of ISO relates the cleanliness of the surface to its visual appearance.
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Jul 16, 0 The overall quality, as well as durability, of paint coatings are affected by the condition of the substrate they are applied on. This is especially concerning when dealing with steel. The surface itself needs to be prepared thoroughly beforehand and, in the case of steel which commonly faces issues pertaining to corrosion and rusting, the surface preparation varies depending upon the different grades of rust, the type of paint selected, the exposure of the finished product and possible environmental concerns.
Some widespread methods of surface preparation used before or even without coating are dry blast cleaning, power tool or hand cleaning, degreasing, and water jetting. All these treatments have individual pros and cons and need to be carefully selected after a suitable assessment on the existing condition of the steel substrate they will be used on. Some notable factors to consider would be rust and mill grades, the profile and presence of contaminants such as oil, water, dust and grease.
The process of identifying different rust grades and the subsequent preparation can be quite arduous and, therefore, the ISO standard was created to act as a guide throughout the process. What is ISO ? ISO is meant to be a pictorial guide to different rust grades at various levels of cleanliness and contains supplementary descriptions via text as well. The standard is divided into 4 parts: ISO — Includes different rust grades and the preparation of both uncoated steel substrates and steel substrates after overall removal of previous coatings.
This section of ISO identifies 4 different rust grades most commonly found on uncoated steel surfaces or on stored steel surfaces.
Specifically, the descriptions of rust refer to these 4 types note that mill scale refers to a flaky blueish surface on hot rolled steel surfaces meant to protect against corrosion : A steel surface mostly covered with the adhering mill scale with little rust if any at all. A steel surface on which the adhering mill scale has largely rusted away from or it can be scraped is severely weakened , but with slight pitting visible under normal vision.
Hand and Power Tool Cleaning Flame Cleaning rarely used ISO — Focuses on steel substrates after the localized removal of their previous paint coatings and their possible preparation processes and grades. This portion of the standard is based upon the prior experience that dictates that the complete removal of previous paint coatings is not always necessary, practical or economical. This holds true especially when regular maintenance is already being carried out and efforts need to be focused on specific portions exposed to a certain pollutant of rust stimulant.
To summarize, ISO proves to be a detailed and helpful guide to identifying various rust grades through different levels of cleanliness of steel substrates.
ISO 8501: Corrosion Protection of Steel Structures by Painting