# ASTM D4752

Source: https://coatmentor.com/standards/astm-d4752/ · Updated 2026-10-14

MEK solvent-rub test for the cure of inorganic zinc silicate primers.

**Publisher**: ASTM International

**Area**: Adhesion, cure and holidays

A cloth soaked in methyl ethyl ketone (MEK) is rubbed back and forth over an inorganic (ethyl silicate) zinc primer for 50 double rubs. A film that softens, or transfers a lot of zinc to the cloth, is not yet cured. Organic coatings have their own rub test, ASTM D5402.

## The rating

- **5:** no effect on the surface and no zinc on the cloth.
- **4:** a burnished area and a little zinc on the cloth.
- **3:** some marring and a visible dent in the film.
- **2:** heavy marring and an obvious dent.
- **1:** a heavy dent, but no penetration to the steel.
- **0:** rubbed through to the steel.

A 5 usually allows topcoating. Agree the rating needed with the coating maker and the specification before the test, not after it.

## Why the weather matters

These primers cure by reacting with moisture in the air, so humidity and temperature set the pace. The FROSIO book gives more than 50 % RH as the need for cure. The same primers mud-crack when applied too thick.

**3** practice items in the members area mention ASTM D4752 (CIP 1: 1 · CIP 2: 1 · FROSIO written: 1).

## Related

- **Concepts:** [Zinc-rich primers](https://coatmentor.com/learn/zinc-rich-primers/) · [Drying, curing and recoat windows](https://coatmentor.com/learn/cure-and-recoat/)
- **Standards:** [ISO 12944](https://coatmentor.com/standards/iso-12944/)
- **Defects:** [Undercure](https://coatmentor.com/defects/undercure/)

## About this page

**Also published openly:** [KTA-Tator: cure testing of inorganic zinc-rich primers](https://kta.com/cure-testing-of-inorganic-zinc-rich-primers/).

This page describes the subject of ASTM D4752 in our own words; it does not reproduce the standard. For the full text, buy the current edition from ASTM International. Checked on 2026-10-14; errors go in the [corrections log](https://coatmentor.com/method/). CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.