The corrosive wear of cast iron under potentiostatically-controlled conditions in sulphuric acid solutions

Observations of steel surfaces under lubricated wear

Effects of dissolved oxygen in saline on corrosive wear of steel

Pin-on-disk wear tests of carbon steels in saline solution were carried out at high loads to study the effects ofmechanical and chemical factors on the transition between severe and mild wear. The factors were load, presliding time, concentration of saline solution, dissolved oxygen content, and applied potential for cathodic protection. Severe wear and seizure appear at low concentration levels of saline solution and the transition takes place at a certain concentration level of saline solution. The concentration level for the transition is higher under argon-saturated condition than under air-saturated condition. Mild wear is predominant over the whole range of dissolved oxygen content from 0.5 to 18 ppm in 0.5 wt percent saline solution and the wear rate decreases with decreasing dissolved oxygen content. The mild wear occurs in the range from 2 to 18 ppm in 0.01 wt percent saline solution, whereas the wear mode moves to severe wear below 2 ppm. Mild wear predominates under incomplete cathodic protection between -0.50 and -0.80 V (versus Ag/AgCl) in 0.5 wt percent saline solution. The applied potential for the transition from initial to steady wear is more negative under higher dissolved oxygen content condition. Complete severe wear occurs below -0.90 V (versus Ag/AgCl) with a risk of seizure.

Influence of Mechanical and Chemical Factors on Transition Between Severe and Mild Wear in Saline Solution

Sliding wear tests of carbon steels were conducted in corrosive environments. The transition from severe to mild wear takes place in ion-exchanged water and saline solution as well as in dry conditions. The severe wear rate is slightly affected by environment. The mild wear rates in liquids are almost constant in the range of low load and increase proportionally to load in the range of high load. The former is due to corrosion fatigue fracture, and the latter is due to the fracture at adhered asperities. Corrosion intensity of liquid produces two opposite effects: one is to promote mild wear loss and the other is to inhibit the occurrence of severe wear.

WEAR BEHAVIORS OF CARBON STEELS IN CORROSIVE ENVIRONMENTS: Part 1, Mild and Severe Wear, and Transition

The wear of carbon steel in corrosive environments has been observed under the potential controlled conditions, and the mechanism of wear and friction in corrosive environments is discussed. In the wear of metals in corrosive environments, the fracture of adhesion points, the fracture by thermal fatigue, the rubbing off of corroded layer and the damage by corrosion fatigue are observed in accordance with the variety of corrosive agents, the corrosion intensity, the type of friction, the rubbing velocity and the contact load. In the oxidizing neutral media, the lubrication due to the corrosion products plays an important role in the behavior of wear, the minimum wear rate being obtained under the mild corrosiveness in the type of face contact. In the reducing acid media, the lubrication of corrosion products is not found because of their dissolution. In the corrosive wear of metals, the wear rate is much affected by the dissolution rate of metals because of the great effect of corrosion fatigue. The cathodic potential sufficient to protect the static corrosion is not adequate to the members under friction in corrosive environments, owing to the increase of the surface activity of metals. However, the protection from corrosion is not always expected to decrease the wear rate as is mentioned above.

Daito Fujita

Papers

Wear of Metals in Corrosive Environments