Contamination on the surface is one thing a coating manufacturer's prep requirements address, and preparing it properly starts with finding out how deep the contamination goes before anyone picks a prep method. This guide explains how oil contamination is assessed, which cleaning and mechanical removal approaches are used, how the prepared surface should be tested before a coating goes down, and when contamination is severe enough that coating is not a realistic option. It does not compare every surface prep method in detail; for that, see the guide comparing concrete surface prep methods. Use this page to understand what questions to ask and what a written scope should include before work begins.
Coatings need a clean, sound, profiled surface; ASTM D4258 covers cleaning and D4259 covers abrasion to remove foreign material and weak laitance before coating. Grease and other foreign material must be removed before coating; ASTM D4258 covers cleaning, D4259 covers abrasion to remove foreign material and weak laitance. Where oil has only sat on the surface, cleaning may remove it.
Before any cleaning or mechanical work begins, the slab should be evaluated for the extent and depth of oil penetration, not just the visible stain pattern.
Cleaning (ASTM D4258) and abrasion (ASTM D4259) are separate practices and may both be part of a scope.
Cleaning practices such as broom cleaning, vacuum cleaning, air blast cleaning, water cleaning, detergent water cleaning, and steam cleaning are described in ASTM D4258, which covers removing grease, dirt, and loose material from concrete before coating. This practice is meant for light-duty coating service and is not intended to change the surface profile of the concrete — it only cleans it. For oil that has only stained the surface and not penetrated, cleaning per this practice may be part of the prep, but it is not a substitute for profiling where a stronger bond is needed.
Where a coating needs optimum bond for service conditions such as mechanical loading or temperature cycling, ASTM D4259 covers abrasion to create a surface profile and remove foreign materials and weak laitance. ASTM D4259 covers abrasion to create a surface profile and remove foreign materials and weak surface laitance; it does not set how deep contamination must be removed.
ICRI 310.2R is the industry guideline for selecting and specifying concrete surface preparation methods for coatings, overlays, and repair, and it summarizes the capabilities, operating requirements, and limitations of the available methods. It also includes benchmark surface profiles, known as CSPs, used as visual standards for specification and verification. To find Colorado concrete surface preparation contractors, see the hub.
A pull-off test per ASTM D7234 measures bond strength of an applied, cured coating on concrete; ask the coating manufacturer what surface-readiness testing its data sheet requires.
ASTM D7234 covers evaluating the pull-off strength of a coating on concrete using a portable adhesion tester, measuring the greatest tensile force a surface can bear before a plug of material detaches. This method is for coatings on concrete specifically; ASTM D4541 is the related method for coatings on metal substrates and should not be used to describe concrete coating adhesion. Because the coating needs to be sufficiently cured before this test is run, confirm the required cure time on the coating manufacturer's data sheet rather than assuming a fixed number of days.
Ask the contractor and the coating manufacturer, in writing, whether the slab can be brought to the condition the coating data sheet requires; the standards discussed here do not set a contamination limit for coating, and the limit, if any, comes from the coating manufacturer's data sheet. Ask your contractor to state plainly, in writing, whether they believe the slab can be brought to a coatable condition with the proposed method, or whether contamination is severe enough that coating is not advisable without further investigation or a different repair approach. For general concrete surface prep cost ranges by city, see the calculator and cost guide. Once the slab is confirmed coatable, you can start comparing coating systems through the Colorado commercial epoxy flooring contractor hub.
Ask how the contractor will evaluate the substrate before selecting a prep method (ICRI 310.2R). Ask your contractor to document this assessment, including photos of the exposed concrete at different depths, before they commit to a single prep method in the written scope.
Cleaning practices described in ASTM D4258 remove grease, dirt, and loose material and are meant for light-duty coating service, but this practice is not intended to change the concrete's surface profile. Where optimum bond is needed, ASTM D4258 says cleaning alone is not intended; see D4259 abrasion.
CSP stands for concrete surface profile, a set of benchmark textures defined in ICRI 310.2R used to specify and verify how rough or aggressive the prepared concrete surface is. Specifying the CSP gives a shared visual benchmark for the surface profile the coating manufacturer requires (ICRI 310.2R chips); it does not verify contamination removal.
Yes, discuss this with your contractor; a D7234 pull-off test on a cured trial patch gives a bond-strength reading at that location; acceptance values come from the coating manufacturer. This test is destructive at the test location and may require a small spot repair, so plan for that in the schedule.
Not always. Some slabs have contamination that is too deep or widespread to remove to sound, oil-free concrete without impractical amounts of material removal, and in that case the contractor should state in writing whether coating is advisable at all.
Scope differences should be itemized in the quote. You can compare estimated costs for different prep scopes using the cost calculator or the dedicated cost guide before finalizing your budget.
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